Date Due • \^&irt'^^^ COR^- UNIVE- LIBR" PRINTED IN GIFT OF Prof. M. L. Nichols CHEKISTRY C9f NO. 23233 PROBLEMS m INORGANIG CHEMISTRY BY L. M. DENNIS JPROFESSOR OF INORGANIC CHEMFSTRY COJRNELlTiaNIVERSITY " /-.>. ?S HH 1^ gll OO OJ ho «pi go boO Ow til KM I" co2 (SM O." O S OO 3J3 Pi Pi 9 3 o< XX TABLE OF METRIC MEASURES WITH ENGLISH EQUIVALENTS Measures of Length 1 Millimeter, mm. 1 Centimeter, cm. 1 Decimeter, dm. 1 Meter, m. 1 Kiolmeter, km. = 10 mm. = 10 cm. = 10 dm. = 100 m. = .03937 inch. = .3937 " = 3.9370 inches. = 39.3708 " = .6214 mile. : 3.2808 feet. 1 Cubic Centimeter, cc. 1 Cubic Decimeter (Liter), 1, = 1000 cc, 1 Cubic Meter Measures of Volume ,06103 cu. inches, or .03381 U. S. fluid oz. .027 cu. inches ,057 V. S. qts. 1000 1. = 35.3166 cu. feet. (61.( ( 1-' or .2642 U. S. gallon. 1 Milligram 1 Gram = 1000 mg. 1 Kilogram (kilo) = 1000 grams. Measures of Weight = .0154 grain. = 1S.432 grains, or .03215 oz. troy, or .03527 oz. av. = 2.2046 lbs. av. Common English Measures with Metric Equivalents 1 Inch = 25.399 millimeters. 1 Foot = .3048 meter. 1 Mile 1.609 kilometers. 1 Cu. inch = 16.386 cubic centimeters. 1 Cu. foot = 28.315 liters. 1 Quart = .9464 " 1 Gallon = 3.7854 " 1 Grain 1 Ounce Av. 1 Lb. Av. 1 Ton (2000 lbs.) = .0648 gram. = 28.3495 grams. = 453.59 grams. = 907.18 kilograms. Apothecaries' Weights and Measures with Metric Equivalents 1 Grain = .0648 gram. 1 Scruple = 1.296 grams. 1 Drachm = 3.888 grams. 1 Oz. Troy = 31.1035 grams. 1 Lb. Troy = 373.2418 grams. 1 Minim = .0616 cc. 1 Fluid Drachm = 3.6965 cc. 1 Fluid Ounce = 29.572 cc. 1 Pint = 473.1 cc. Area 10,000 Square Centimeters = 1 sq. meter = 10.764 sq. ft. 1 Square Centimeter = .1550 square inch. 1 Square Foot = .0929 square meter. 1 Square Inch = 6.4516 square centimeters CONVERSION FACTORS To Change To Multiply by ] Inches Centimeters 2.54 Feet Meters .305 Miles Kilometers 1.609 Meters Inches 39.37 Kilometers Miles .621 Square inches Square centimeters 6.452 Square yards Square meters .836 Square centimeters Square inches .155 Square meters Square yards 1.196 Cubic inches Cubic centipieters 16.386 Cubic yards Cubic meters .765 Cubic centimeters Cubic ipches .061 Cubic meters Cubic yards 1.308 Fluid ounces Cubic centimeters 29.572 Quarts Liters .946 Cubic centimeters Fluid ounces .034 Liters Quarts 1.057 Grains Milligrams 64.799 Ounces (av.) Grams 28.35 Pounds (av.) Kilograms .454 Oimces (troy) Grams 31.103 Grams Grains 16.432 Kilograms Poimds 2.205 THEORETICAL DENSITIES OF GASES AND WEIGHT OF ONE LITER OF EACH at 0° and 760 mm. pressure Weight of Molecular Density I LITER IN Substance Formula Weight AlR = I GRAMS Lati- tude 45° AT SEA-LEVEL Acetylene C.H, 26.02 0.898 1.162 Ammonia NH3 17.03 0.589 0.762 Arsine AsH, 78.02 2.696 3.485 Bromine Br, 159.92 5.525 7.143 Butane C^H.^ 58.08 2.006 2.594 Carbon dioxide CO, 44.00 1.520 1.965 Carbon monoxide CO 28.00 0.967 1.251 Carbon oxysulphide COS 60.06 2.075 2.682 Carbonyl chloride COCl, 98.90 3.417 4.417 Chlorine CI, 70.90 2.449 3.167 Cyanogen C,N, 52.02 1.799 2.326 Ethane C,H, 30.05 1.038 1.342 Ethylene C,H, 28.03 0.968 1.252 Hydrogen H= 2.016 0.069 0.0899' Hydrogen bromide HBr 80.97 2.797 3.616 Hydrogen chloride HCl 36.46 1.259 1.628 Hydrogen fluoride HP 20.00 0.691 0.894 Hydrogen iodide HI 127.98 4.417 5.711 Hydrogen sulphide H,S 34.08 1.177 1.523 Methane CH, 16.03 0.554 0.716 Nitric oxide NO 30.01 1.038 1.342 Nitrogen N, 28.02 0.970 1.254 Nitrous oxide N,0 44.02 1.523 1.969 Oxygen 0, 32.00 1.105 1.429 Phosphine PH3 34.02 1.175 1.520 Propane C3H3 44.06 1.522 1.966 Propylene C3H, 42.05 1.453 1.878 Sulphur dioxide SO, 64.06 2.213 2.861 Water vapor H,0 18.016 0.622 0.804 Atmospheric air 1.000 1.293 'In answering the problems in this book, use 0.09 gram as the weight of one liter of hydrogen. CHEMICAL PROBLEMS CORRECTION OF GAS VOLUMES If a gas at 0°C. be warmed to 1 C. (the pressure remaining the same) it will expand Vzis of the volume that it occupied at 0°. For each additional rise of 1°C. there will be an increase in volume of ¥273 of the volume of the gas at 0°. Consequently, if the tem- perature of a gas is raised from 0°C. to 273°C. its volume will be doubled. If a gas be cooled from 0°C. to — 1°C. there will be a decrease of V273 of its volume, and for each additional fall of 1°C. there will be a decrease in the volume of %73 of the volume of the gas at 0°. Consequently it would seem that if a gas-were cooled down to 273° below the Centigrade zero, its volume would be zero. This is manifestly impossible, yet for convenience we use this temperature, — 273°C., as the starting point in temperature calculations and term it the absolute zero. Temperatures measured from this absolute zero are termed absolute temperatures. Thus, 0°C. is 273° above zero in terms of absolute temperature. Law of Charles. Provided the pressure remains constant, the volume of a gas varies directly as its absolute temperature. If T and Ti be two different absolute temperatures and V and Fi be the volumes of a gas corresponding to these temperatures, then (1) V:Vi=T:Ti Again, the volume of a gas changes as the pressure to which it is subjected is changed. Law of Boyle. Provided the temperature remains constant, the volume of a gas is inversely proportional to the pressure. If P and Pi be two different pressures and V and Vi be the volumes of a gas corresponding to these pressures, then (2) Y.v, = P,:P Volumes of ga,ses can not be compared unless the temperature and pressure under whidb the gases were measured are stated, or unless the volumes are corrected according to some arbitrary standard. The latter is the simpler procedure and consequently it is employed. The arbitrary standard adopted by scientists in 10 stating the volume of a gas is the volume that the gas would occupy under "standard conditions," that is, at a temperature of 0°C. (273° absolute temperature) and under a pressure of 760 milli- meters of mercury. In reducing an observed gas volume to the volume which the gas would occupy if under standard conditions, the following procedure may be used. If V represents the volume under standard conditions, V\ the observed volume, T the absolute temperature under standard conditions (273°), and Ti the observed absolute temperature, then from (1) we may ascertain the volume that a gas at a temperature Ti would occupy at the standard temperature T, by multiplying the observed volume by If P represents the standard pressure (760 mm.) and Pi the observed barometric pressure, we may ascertain the volume that the gas would occupy at standard pressure by multiplying the observed volume by Pi P To make these two corrections simultaneously, it is only neces- sary to multiply the observed volume by both of these expressions. T P (3) V-V,~ p Suppose, for example, one were asked to ascertain the volume, under standard conditions, of a gas that measures 110 cc. at 57° C. and under a pressure of 740 mm. In this case Fi = 110; r = 273; Ti = 330 (since 57° C. is 330 above the absolute zero); P = 760; and Pi = 740. Substituting these values in (3) 273 X 740 ^-"° SWXWO =88-6c«- Conversely, if we know the volume (V) of a gas measured under standard conditions, and wish to ascertain what volume (Vi) it would occupy at any other temperature and pressure, we may use the following equation which is derived directly from (3). 11 T P (4) Fi = Vj,' p^ 1. A volume of air at 0° measures 90 cc. What would be its volume at 182°? Ans. 150 cc. 2. A volume of air at 182° measures 125 cc. At what temper- ature would the volume be 100 cc? Ans. 91°. 3. A volume of air at 91° measures 800 cc. What would be its volume at standard temperature? Ans. 600 cc. 4. If a gas be cooled from +91° to — 91°, to what extent will its volume contract? Ans. }4. 5. An open vessel is heated from 0° to 546°. What portion of the air that it at first contained now remains? Ans. y^. 6. A volume of air at 45.5° measures 70 cc. What would be its volume at 91°? Ans. 80 cc. 7. 360 cc. of air at 0° is warmed to 22^°. What is then its volume? Ans. 390 cc. 8. 360 cc. of oxygen at 10° is warmed to 22^°- What is then its volume? Ans. 376.2 cc. 9. To what temperature must one liter of hydrogen at +87° be cooled to reduce its volume to 500 cc. ? Ans. — 93°. 10. A volume of air at 17° measures 290 cc. What would be its volume at 77°? Ans. 350 cc. 11. A volume of oxygen at +27° measures 150 cc. What would be its volume at — 23°? Ans. 125 cc. 12. A volume of air at 0° measures 1 liter; what would be its volume at 18°? Ans. 1065.9 cc. 13. A volume of air measures 90 cc. under a pressure of 760 mm. What would be the volume under a pressure of 570 mm. ? Ans. 120 cc. 14. A sample of hydrogen measures 102 cc, the pressure being 750 mm. What would be the volume of the gas if the pressure were changed to 765 mm. Ans. 100 cc. 15. A volume of air measures 9 liters at a pressure of 780 mm. At what pressure would its volume be 10 liters? Ans. 702 mm. 12 16. If 10 liters of hydrogen, measured at standard pressure, were forced into a cylinder of one liter capacity, what pressure would the gas then exert? Ans. 7.6 meters. 17. A volume of gas that measured 170 cc. at 740 mm. pressure was afterwards found to measure 185 cc. What was the height of the barometer at the time of the second measurement? Aqs. 680 mm. 18. A volume of gas measures 150 cc. when the barometer stands at 745 mm. What would be the volume at standard pres- sure? Ans. 147.04 cc. 19. A volume of hydrogen measured 200 cc. when the barom- eter stood at 768 mm. What would be the volume at 755 mm. pressure? Ans. 203.44 cc. 20. The air in a bottle is pumped out until the pressure drops from 750 mm. to 150 mm. What portion of the air has been removed? Ans. %. 21. A volume of nitrogen in a eudiometer tube over mercury measures 62 cc, the mercury in the tube standing at a height of 8.3 cm.; the barometer stands at 75.8 cm. Reduce the volume to standard pressure. Ans. 55.07 cc. 22. A eudiometer tube contains a volume of gas measuring 102 cc; the mercury outside the tube stands 17 cm. above the level on the inside, the barometer indicating meanwhile a pressure of 740 mm. Reduce the volume to standard pressure. Ans. 122.13 cc. 23. A volume of gas in a eudiometer measures 242 cc. The mercury in the tube stands 18 mm. above that outside. Barometer 740 mm., temperature, 18°C. Reduce to standard volume. Ans. 215.68 cc. 24. A volume of gas in a tube measures 72 cc. The mercury nthe tube stands at the same level as that on the outside. Barom- ieter, 737 mm.; temperature, 17°C. What would be the volume under standard conditions? Ans. 65.7 cc. 25. The volume of gas in a eudiometer measures 68 cc, the level of the mercury in the tube and trough being the same. The barometer indicates an atmospheric pressure of 739 mm. The 13 temperature is 20°C. What would be the volume of the gas at 0°C. and under 760 mm. pressure? Ans. 61.61 cc. 26. The volume of gas contained in a tube measures 76 cc. The mercury in the tube stands at a height of 17 mm. Barometer indicates a pressure of 752 mm. The temperature is 17°C. What would be the volume of the gas under standard conditions? Ans. 69.19 cc. 27. The volume of a gas contained in a tube measures 86 cc, the mercury standing at a height of 34 mm. in the tube. Baro- metric pressure, 742 mm.; temperature, 23°C. What would be the volume of the gas under standard conditions? Ans. 73.89 cc. 28. One liter of oxygen at 0° and 760 mm. pressure weighs 1.429 grams. What will one liter weigh at the same temperature with the barometer standing at 780 mm.? Ans. 1.466 grams. 29. What will be the weight of one liter of oxygen at 0° under a pressure of 740 mm.? Ans. 1.392 grams. 30. At what pressure will one liter of oxygen at 0° weigh one gram? Ans. 531 mm. 31. What will be the weight of one liter of oxygen at 18° and with the barometer at 730 mm. ? Ans. 1 .288 grams. 32. Under standard pressure, at what temperature will 1 liter of oxygen weigh 1 gram? Ans. 117.1°. 33. Under standard temperature, at what pressure will one liter of hydrogen weigh one gram? Ans. 8444.4 mm. 34. One liter of air at standard pressure and temperature weighs 1.293 grams. Under what pressure will the same volume weigh 2 grams? Ans. 1175.5 mm. 35. If steam is passed over red-hot iron and six grams of hydrogen is set free, what weight of water has been decomposed? Ans. 53.62 grams. 36. If 200 grams of steam is passed over red-hot iron, what weight of hydrogen will be set free? Ans. 22.38 grams. 14 37. A tube containing copper oxide weighs 75 grams. This tube is heated to redness, and hydrogen is passed through it. When cooled, the tube is again weighed, and its weight is now found to be 72 grams. What weight of hydrogen has united with the oxygen of the copper oxide? What weight of water has been formed? Ans. Weight of hydrogen, 0.378 gram. Weight of water, 3.378 grams. 38. Hydrogen is passed over hot copper oxide as in the preced- ing problem, and the water that is formed is absorbed by calcium chloride and its weight ascertained to be three grams. What has been the loss of weight of the tube containing the copper oxide? Ans. 2.66 grams. 39. If a tube containing copper oxide weighs, before hydrogen is passed through it, 15.846 grams, and after the hydrogen has been passed, 12.239 grams, how many liters of hydrogen have united ■with the oxygen of the copper oxide? Ans. 5.049 liters. How much water has been formed? Ans. 4.061 grams. WEIGHT AND PERCENTAGE COMPOSITION Each chemical element is represented by a symbol. The symbol denotes an atom of the element. The actual weights of the atoms have not been ascertained, but we do know their relative weights referred to the weight of an atom of oxygen. These rela- tive weights of the atoms of the elements are termed the atomic weights of the elements. (See Table of Atomic Weights on page 3.) The atomic weight of oxygen is 16, and that of hydrogen is 1.008. A molecule of water consists of two atoms of hydrogen united to one atom of oxygen and is represented by the formula H2O. Consequently, water is made up of 2 X 1.008 = 2.016 parts by weight of hydrogen and 16 parts by weight of oxygen. A molecule of hydrogen chloride (HCl) is made up of 1.008 parts by weight of hydrogen, and 35.46 (the atomic weight of chlorine) parts by weight of chlorine. A molecule of potas.sium chlorate (KCIO3) is made up of 39.10 (the atomic weight of potassium, K) parts by weight of potassium, 35.46 parts by weight of chlorine, and 3 X 16 =48 parts by weight of oxygen. The sum of the weights of all the atoms in a compound is termed the molecular weight of the compound. When substances undergo chemical change, there are formed other substances possessing properties different from those of the original bodies. A chemical equation is a brief expression of chemical change. Since matter is never created nor destroyed, it follows that the total weight of the reacting substances must equal the total weight of the products of the reaction, or, in other words, the number of atoms of each element must be the same on both sides of the equation. For example, when hydrochloric acid is added to a solution of sodium hydroxide, the reaction may be expressed by the equation : NaOH + HCl = NaCl + H2O. The equation indicates not only that sodium hydroxide and hydrochloric acid react to form sodium chloride and water, but also that 23 + 16 + 1.008 = 40.008 parts by weight of NaOH, and 1.008 + 35.46 = 36.468 parts of HCl, combine to form 23 + 35.46 = 58.46 parts NaCl and 2.016 + 16 = 18.016 parts 16 HaO. If now we wish to know how much sodium chloride may be prepared from any given weight, say 100 grams, of sodium hydrox- ide by adding hydrochloric acid to the latter, we use the simple proportion 40.008 : 58.46 = 100 : x. x = 146.1 grams. In similar manner we may calculate the weight of a product resulting from other cases of chemical change, or, conversely, the weight of the reacting substance needed to yield a given weight of a product. If a product of a reaction is gaseous imder standard conditions, the volume of that product may be ascertained by first calculating the weight of the substance that is produced and then dividing this weight by the weight of a unit volume of the substance. For example, to find what number of liters of hydrogen is produced when 100 grams of water is decomposed by electrolysis, the weight of the hydrogen that is formed is first calculated from the propor- . tion H2O (2.016 + 16 = 18.016) : 2 H (2.016) = 100 : x. x =11.19 grams. One liter of hydrogen under standard conditions weighs .0899 gram. Consequently, 11.19 grams of hydrogen would, under standard conditions, have a volume of 124.47 liters. 17 NOTE: — ^In answering the problems use 0.09 gram as the weight of one liter of hydrogen. 40. What weight of hydrogen can be obtained from 18.016 grams of water? Ans. 2.016 grams. 41. What volume of hydrogen can be obtained from 900.8 grams of water? Ans. 1120 liters. 42. What weight of hydrogen can be obtained from 10 grams of water? Ans. 1.119 grams. 43. What volume of hydrogen can be obtained from one kilogram of water? Ans. 1243.33 liters. 44. With what weight of hydrogen will 30 grams of oxygen unite to form water? Ans. 3.78 grams. 45. What volume of hydrogen results when 18 grams of zinc is treated with sulphuric acid? Ans. 6.16 liters. 46. With how much sulphuric acid must zinc be treated in order to obtain 16250 cc. of hydrogen. Ans. 71.15 grams. 47. What weight of zinc sulphate would be formed in the preceding? Ans. 117.13 grams. 48. What volume of hydrogen would be evolved when zinc reacts with a solution of hydrochloric acid that contains 327 grams of hydrogen chloride? What weight of zinc chloride will be formed? Ans. 100.45 liters. 611.25 grams Zn CI2. 49. A balloon of 100,000 liters capacity is to be filled with hydrogen; how many kilograms of zinc and sulphuric acid will be needed? Ans. Zn, 291.3 kilograms; H2SO4, 437.8 kilograms. 50. How much water could be decomposed by 20.7 grams of sodium, and what volume of hydrogen would be set free? Ans. 16.2 grams H2O, 10.08 liters of hydrogen. 51. What volume of hydrogen will unite with 24 grims of oxygen to form water? Ans. 33.6 liters. 52. What volume of hydrogen and of oxygen could be obtained by electrolysis of 10 grams of water? Ans. 6.22 liters oxygen. 12.43 liters hydrogen. 53. If 23 grams of sodium acts upon water, what volume of hydrogen will be produced? Ans. 11.1 liters. 18 54. What weight of sodium would be needed to produce, by the decomposition of water, one liter of hydrogen? Ans. 2.058 grams. 55. What weight of oxygen can be obtained by heating 54 grams of mercuric oxide, HgO? Ans. 4 grams. 56. How much mercuric oxide must be heated in order to obtain 2 grams of oxygen.? Ans. 27 grams. 57. With what weight of mercury will 16 grams of oxygen unite to form mercuric oxide? Ans. 200 grams. 58. What weight of oxygen is contained in 25 grams of potas- sium chlorate, KCIO3? Ans. 9.78 grams. 59. Calculate the percentage of oxygen by weight in mercuric oxide, HgO; manganese dioxide, Mn02; potassium chlorate, KCIO3; and water, H2O. Ans. HgO, 7.41 per cent; KCIO3, 39.15 per cent; MnOs, 36.78 per cent; H2O, 88.81 per cent. 60. What weight of potassium and what weight of chloriae are contained in 17 grams of potassium chlorate? Ans. K = 5.43 grams, CI = 4.91 grams. 61. How much potassium chloride would result upon highly heating 35 grams of potassium chlorate? Ans. 21.3 grams. 62. How much potassium chlorate must be heated in order to obtain 14 grams of oxygen? Ans. 35.76 grams. 63. How much potassiun chlorate must be used to fill a gaso- meter of ten liters capacity with oxygen, when the temperature is 20° and the barometric pressure is 750 mm. ? Ans. 33.52 grams. 64. If potassium chlorate costs 80 cts. per kilogram, what will be the cost of enough to make 500 grams of oxygen gas? Ans. $1.02. 65. What weight of sodium will be necessary to decompose 15 grams of water? Ans. 19.19 grams. What weight of hydrogen will be formed? Ans. 1.68 grams. 66. What weight of phosphorus would be needed to combine with 700 cc. of oxygen to form phosphorus pentoxide, P2O5? Ans. 0.77 gram. 19 67. If one gram of hydrogen and one gram of oxygen are mured and the mixture then ignited, what weight of water will be formed? What volume of gas will remain uncombined? Ans. 1.126 grams; 9.71 liters. 68. What weight of oxygen will unite to form water with a volume of hydrogen that measures 1250 cc. at 740 mm. and 18°C.? Ans. 0.8155 gram. 69. A glass tube containing copper oxide weighed 56.5 grams. After heating it to redness and passing hydrogen through it imtil all the CuO was reduced to metal, the weight of the tube and con- tents was found to be 48.5 grams. What weight of water was formed, and how much copper oxide did the tube at first contain? Ans. H2O, 9.008 grams; CuO, 39.8 grams. 70. If 10 cc. of water is completely decomposed by electrolysis in a room in which the pressure is 755 mm., and the temperature is 21°C., what will be the volume of the hydrogen that is formed? Ans. 13.48 liters. 71. How much weight will 32.2 grams crystallized sodium sulphate, Na2S04 ■ 10 H2O, lose on heating? Ans. 17.99 grams. 72. How many grams of dry sodium carbonate is contained in one pound of crystallized washing soda, Na2CO3l0 H2O? Ans. 168.25 grams. 73. How many pounds of Plaster of Paris, (CaS04) 2' H2O can be made by calcining 10 kilograms of gypsum, CaS04- 2 H2O? Ans. 18.59 pounds. 74. How many kilograms of water mil be set free when one ton of crystallized copper sulphate, CUSO4 • 5 H2O, is converted to the anhydrous condition by heating? Ans. 327.51 kilograms. 75. What weight of nitric acid will be produced by highly heating 75 grams of Chile saltpeter, NaNOa, with an excess of con- centrated sulphuric acid? Ans. 55.56 grams. 76. What weight of sulphuric acid and sodium nitrate should be taken in order to obtain 215 grams of nitric acid? NaNOs + H2SO4 = NaHS04 + HNO3. Ans. H2SO4, 334'.61 grams. NaNOs, 290.2 grams. 20 77. What weight of primary sodium sulphate will be formed in the preceding reaction? Ans. 409.81 grams. 78. From what weight of potassium nitrate can 25 grams of nitric acid be obtained by treatment with sulphuric acid? Ans. 40.13 grams. 79. If 78 grams of copper nitrate, Cu (N03)2, is decomposed by concentrated sulphuric acid, what weight of nitric acid and what weight of copper sulphate will be formed? Ans. 52.397 grams HNO3. 66.376 grams CUSO4. 80. If copper and nitric acid react as expressed in the equation : 3 Cu + 8 HNO3 = 3 Cu (N03)2 + 2 NO + 4 H2O, what weight of metallic copper should be taken if one kilogram of copper nitrate is to be formed in this manner? Ans. 338.98 grams. 81. What weight of metallic copper will be needed to produce 10 liters of nitric oxide? Ans. 42.66 grams. 82. What volume of nitric oxide, measured at 743 mm. and 18° C, will be produced by treating 18 grams of metallic copper with an excess of nitric acid? Ans. 4.6 liters. 83. What weight of nitrogen tetroxide, N2O4, will result when 3300 cc. of nitric oxide, NO, is brought into contact with an excess of oxygen? Ans. 6.79 grams. 84. What weight of nitrous oxide, N2O, will be formed by heatiag 50 grams of ammonium nitrate? Ans. 27.49 grams. How many grams of water will be produced? Ans. 22.50 grams. 85. What weight of ammonium nitrate must be taken to yield upon heating one liter of nitrous oxide? Ans. 3.58 grams. 86. What weight of ammonia, NH3 will result upon decom- posing 50 grams of ammonium chloride with slaked lime? Ans. 15.92 grams. 87. What volume of ammonia may be obtained from 430 grams of ammonium chloride? Ans. 179.7 liters. 21 88. If one volume of water absorbs at 20° C. 650 volumes of ammonia, what weight of ammonia at 20° will be taken up by one liter of water at that temperature? Ans. 461.6 grams. 89. What weight of potassium hydroxide will neutralize 36.46 grams of hydrogen chloride? Ans. 56.1 grams. 90. What weight of sodium hydroxide will neutralize 36.46 grams of hydrogen chloride? Ans. 40 grams. 91. What weight of potassium hydroxide will neutralize 63 grams of nitric acid? Ans. 56.1 grams. 92. What weight of sodium hydroxide will neutralize 63 grams of nitric acid? Ans. 40 grams. 93. What weight of potassium hydroxide will neutralize 98 grams of sulphuric acid? Ans. 112.2 grams. 94. What weight of sodium hydroxide will neutralize 98 grams of sulphuric acid? Ans. 80 grams. 95. If 23 grams of sodium is thrown upon water, what weight of sodium hydroxide wiU be formed? Ans. 40 grams. 96. If 10 grams of metallic sodium is thrown upon water, what weight of sodium hydroxide will be formed? Ans. 17.38 grams. 97. What weight of nitric acid will exactly neutralize 40 grams of sodium hydroxide? Ans. 63 grams. 98. If 40 grams of sodium hydroxide is dissolved in one liter of water, what weight of nitric acid will be required to neutralize 500 cc. of the solution? Ans. 31.5 grams. 99. If one liter of a solution of nitric acid in water contains 6.3 grams of the acid, what weight of sodium hydroxide will neutraHze 20 cc. of the solution? Ans. 80 milligrams. 100. A solution of sodium hydroxide contains 20 grams of the substance in one liter. A solution of nitric acid contains 126 grams of the acid in one liter. How many cc. of the solution of sodium hydroxide will be required to neutralize 12 cc. of the acid? Ans. 48 cc. 101. What weight of nitric acid will exactly neutralize the sodium hydroxide formed in No. 96, and what weight of sodium nitrate will result? Ans. 27.33 grams HNO3. 36.90 grams NaNOs. 102. What weight of sodium hydroxide will exactly neutralize a solution containing 34 grams of hydrogen chloride? Ans. 37.36 grams. 7 103. What amounts of sodium hydroxide and hydrogen chloride would be needed to yield 75 grams of sodium chloride? Ans. 51.36 grams NaOH. 46.74 grams HCl. 104. If one liter of a solution of sodium hydroxide contained 25 grams of sodium hydroxide, how many grams of nitric acid would be needed to exactly neutraUze 60 cc. of the solution? Ans. 3.3 grams. y 105. If a sample of hydrochloric acid contains 44 grams of hydrogen chloride to the liter, how many cubic centimeters of the solution will be needed to neutralize 20 cc. of the solution of sodium hydroxide mentioned in the preceding question? Ans. 14.48 cc. 106. What weight of sodium hydroxide will neutralize 98 grams of sulphuric acid? What weight of potassium hydroxide will neutraUze the same? Ans. NaOH, 80 grams. KOH, 112.2 grams. 107. If in neutralizing a certain amount of nitric acid with sodium hydroxide, 7.85 cc. of water is formed, how much nitric acid and how much sodium hydroxide have been employed? Ans. 27.46 grams of HNO3. 17.45 grams of NaOH. 108. How many grams of a 5 per cent, solution of KOH will be required to neutralize 10 grams of a 10 per cent, solution of H2SO4? Ans. 22.9 grams. •' 109. 10 grams of commercial caustic soda, dissolved in water, required 116.3 grams of a 10 per cent, sulphuric acid to neutrahze the solution. What percentage of NaOH did the substance con- tain? Ans. 95 per cent. 23 110. 10 grams of commercial nitric acid was exactly neu- tralized by the addition of 58.6 grams of a 10 per cent, solution of potassium hydroxide. What was the strength of the acid in HNO3? Ans. 65.76 per cent. 111. If a solution contained 50 grams of ammonium hydroxide to the liter, how many cubic centimeters of hydrochloric acid con- taining 100 grams of hydrogen chloride to the liter will be needed to neutralize 60 cc. of the ammonium hydroxide solution? Ans. 31.2 cc. 112. What weight of zinc sulphate will be formed upon treat- ing 13 grams of zinc with sulphuric acid? Ans. 32.09 grams. 113. What weight of zinc sulphate will be formed when 98 grams of sulphuric acid acts on zinc? Ans. 161.37 grams. 114. What volume of chlorine can be obtained from 58.46 grams of salt? Ans. 11.1 liters. 115. How many liters of chlorilie can be obtained from 34 grams of salt? Ans. 6.51 liters. 116. How much common salt will be needed to yield 10 liters of chlorine on treatment with manganese dioxide and sulphuric acid? Ans. 52.26 grams. 117. How many liters of chlorine can be obtained by treating 50 grams of manganese dioxide with hydrochloric acid? Ans. 12.87 liters. 118. How much manganese dioxide will be required to liberate 13 liters of chlorine from hydrochloric acid? Ans. 50.52 grams. 119. What weight of chlorine will be set free at the anode upon the electrolysis of a solution containing 65 grams of potassium chloride, KCl? Ans. 30.89 grams. 120. What weight of potassium hydroxide, KOH, would be formed in the preceding reaction? Ans. 48.93 grams. 121. What weights of salt, manganese dioxide and sulphuric acid would be required to produce one cubic meter of chlorine? Ans. 3886.2 grams Mn02. 5226.2 grams NaCl. 8761.8 grams H2SO4. 24 122. What weight of hydrogen chloride would result upon burning one liter of hydrogen in an atmosphere of chlorine? Ans. 3.255 grams. 123. An ore contams 67.4 per cent, of manganese dioxide. What volume of chlorine would result upon treating one ton of this ore with hydrochloric acid? Ans. 157.47 cubic meters. 124. What weight of caustic potash will neutralize 100 hters of hydrogen chloride? Ans. 250.76 grams. 125. At 0° one volume of water will absorb 500 times its own volume of hydrogen chloride. How much will 500 grams of water at 0° increase in weight by absorbing hydrogen chloride to satura- tion? Ans. 407 grams. 126. What weight of hydrogen chloride can be obtained from 25 pounds of salt? Ans. 15.58 pounds. 127. What weight of sodium sulphate would be formed in the preceding reaction? Ans. 30.38 pounds. 128. What weight of hydrogen bromide would be neutralized by 40 grams of sodium hydroxide? Ans. 80.9 grams. 129. WTiat weight of hydrogen iodide would be neutralized by 20 grams of sodium hydroxide? Ans. 63.96 grams. 130. What weight of hydrogen bromide would be formed by treating 18 grams of sodium bromide, NaBr, with dUute sulphuric acid? Ans. 14.15 grams. 131. What weight of hydrogen bromide would result if one cubic meter of hydrogen were caused to unite with bromine vapor by passing the mixture over a catalytic agent? Ans. 7229.3 grams. 132. To obtain 15 grams of bromine how much manganese dioxide, potassium bromide and sulphuric acid should be used? Ans. Mn02, 8.16 grams. KBr, 22.34 grams. H2SO4, 18.40 grams. 25 133. To obtain 15 grams of iodine, how much manganese dioxide, potassium iodide and sulphuric acid will be required? Ans. Mn02, 5.14 grams. KI, 19.63 grams. H2SO4, 11.59 grams. 134. What weight of hydrogen fluoride, HF, would be evolved upon treating 36 grams of calcium fluoride, CaF2, with sulphuric acid? Ans. 18.45 grams. GAS VOLUMES AND MOLECULAR WEIGHTS Equal volumes of gases (under identical conditions of tempera- ture and pressure) contain the same number of molecules. (Avo- gadro's Hypothesis.) Consequently (1) The weights of equal volumes of gases are proportional to the molecular weights of the gases. Using hydrogen chloride and ammonia as an illustration : 36.468 : 17.034 = 1.628 : .762 (Mol. wt. HCl) (Mol. wt. NH3) (Wt. 1 liter HCl) (Wt. 1 liter NH3) The molecule of oxygen contains two atoms; hence the mole- cular weight of oxygen is 32. If the weight of one liter of oxygen (1.429 grams) is known, the weight of a given volume of any gas of known molecular weight may be calculated, because the ratio between the molecular weights of oxygen and the gas in question will be the same as that between the weights of equal volumes of the two gases. For example, the weight of one liter of a gas of molecular weight 44 may be determined from the proportion 32 : 44 = 1.429 : x (Mol. wt. oxygen) (Mol. wt. of (Wt. 1 liter (Wt. 1 liter of other gas) oxygen) other gas) Expressed in other words — • (2) The weight of one liter of any gas is equal to its molecular 1.429 weight multiplied by - 32 Conversely, if the weight of one liter of a gas is known, its molecular weight may be determined from the proportion Wt. 1 liter oxygen : Wt. 1 liter of the gas = Mol. wt. of oxygen : Mol. wt. of the gas, (3) The molecular weight of any gas is equal to the weight of 32 one liter of it multiplied by 1.429 27 The density of a gas is frequently referred to air as unity instead of to oxygen. One liter of air weighs 1.293 grams and con- 1.293 sequently is ' - or .905 as heavy as oxygen. Since the mole- cular weight of oxygen is 32 and since (1) the molecular weights and the actual weights of equal volumes of gases are directly proportional, — (4) The molecular weight of a gas is equal to its density (referred to air) X (.905 X 32) = 28.96. One Hter of oxygen weighs 1.429 grams. Its molecular weight is 32. A weight in grams of the gas equal to its molecular weight (i. e. 32 grams) will possess a volume (under standard conditions) of 32 . . -— — — = 22.39 liters. In round numbers 22.4 liters. 1.429 Similarly, the molecular weight of hydrogen chloride in grams, 36.468 divided by the weight of one liter of the gas, -ir ' equals 22.4. T ., i^ • IT'-OS (Mol. wt.) In the case 01 ammonia i^^rTfTTirr^T^ \ = 22.4; .762 (Wt. 1 liter) ' 30.01 (Mol. wt.) nitric oxide , „,^ ,.!■- — — pr — r- = 22.4; 1.342 (Wt. 1 liter) ' 2.016 (Mol. wt.) hydrogen .0899 (Wt.l liter) = 22-^' 28.02 ( Mol. wt.) „.. nitrogen UsTm^T^te^ = ^^-'^^ These facts may briefly be expressed as follows: — (5) The volume occupied by the molecular weight of a gas in grams, under standard conditions, (termed the gram-molecular volume) is always the same^namely][22.4 liters. 28 molecular weight of a gas Now if = 22.4 it follows that weight of one liter of the gas molecular weight of a gas = weight of one liter of the 22.4 gas. In other words, (6) The weight of one liter of a gas may be determined by dividing its molecular weight in grams by 22.4. 135. How many liters of oxygen would be required to burn 10 liters of hydrogen sulphide.? Ans. 15 liters. 136. What volume of oxygen would be required to burn 10 liters of marsh gas, CH4? Ans. 20 liters. 137. What volume of oxygen would be required to burn 10 liters of carbon monoxide, and what volume of carbon dioxide would be formed? Ans. 5 liters oxygen and 10 liters carbon dioxide. 138. How many liters of oxygen will combine with ten liters of nitric oxide, and what volume of nitrogen peroxide will be formed? Ans. 5 liters oxygen and 10 liters nitrogen peroxide. 139. If nitrogen and hydrogen could be made to combine completely, what volume of each would be required to form 10 liters of gaseous ammonia? Ans. 5 liters nitrogen and 15 liters hydrogen. 140. What volume of hydrogen and of oxygen at 100° would combine to form one liter of steam? Ans. 1 liter hydrogen; 3^ liter oxygen. 141. What volume of hydrogen and of chlorine would combine to form 100 cc. of hydrogen chloride? Ans. 50 cc. of each. 142. In a eudiometer 88 cc. of hydrogen and 132 cc. of chlorine are exploded by a spark. What volume of hydrogen chloride is formed, and what volume of uncombined gas will remain? Ans. 176 cc. hydrogen chloride, and 44 cc. chlorine. 143. What volume of oxygen is required to completely burn 10 liters of benzene vapor, CeHo? Ans. 75 liters. 144. What volume of oxygen is required to burn to carbon dioxide and water 1 liter of the vapor of alcohol, C2H6O? Ans. 3 liters. 145. What volume of oxygen is required to completely burn 175 cc. of acetylene, C2H2? Ans. 437.5 cc. 146. If ammonia and chlorine react to form nitrogen and hydrogen chloride, what volume of chlorine is required to com- pletely react with 6 liters of ammonia and what volume of nitrogen and hydrogen chloride result.'' Ans. 9 liters chlorine. 3 liters nitrogen. 18 liters hydrogen chloride. 147. If there is introduced into a tube that contains 300 cc. of chlorine an amount of ammonium hydroxide more than sufficient to react with the chlorine, and the excess of ammonium hydroxide is then neutralized with dilute sulphuric acid, what gas remains in the tube and what is its volume? Ans. Nitrogen. 100 cc. 148. Calculate the weight of one liter of each of the following gases, applying the method stated in (6) on page 28. a. chlorine b. nitrogen c. sulphur dioxide d. nitrous oxide e. nitric oxide f. ethane g. butane h. hydrogen chloride i. carbon monoxide j. carbon dioxide k. marsh gas 1. phosphine Applying the method stated in (3) on page 26, calculate the molecular weights of the following gases. 149. One liter of ethane weighs 1.342 grams. 150. One liter of hydrogen sulphide weighs 1.523 grams. 151. One liter of hydrogen bromide weighs 3.616 grams. 152. 232 cc. of phosphine weighs .3526 gram. 153. One liter of carbonyl chloride weighs 4.417 grams. 30 154. One liter of nitrous oxide weighs 1.969 grams. 155. 350 cc. of butane weighs .9079 gram. Applying the method stated in (4) on page 27 calculate the molecular weights of the following gases : 156. The density (referred to air) of ammonia is .589. 157. The density (referred to air) of hydrogen fluoride is 0.691. 158. The density (referred to air) of bromine vapor is 5.525. 159. The density (referred to air) of mercury vapor is 6.98. 160. The density (referred to air) of gaseous hydrogen iodide is 4.'417. 161. Calculate the density (referred to air) of ethylene, C2H4. Ans. .968. 162. Calculate the density (referred to air) of propane, CsHg. Ans. 1.522. 163. Calculate the density (referred to air) of sulphur dioxide, SO2. Ans. 2.213. 164. How many liters of carbon dioxide would result from burning 5.384 grams of carbon? Ans. 10.046. 165. What volume of oxygen will be required to burn one kilogram of carbon? Ans. 1866.08 liters. 166. What volume of air, of 21 per cent, oxygen by volume, is needed to burn completely one ton of anthracite coal, assumed to be pure carbon? Ans. 8068.6 cubic meters. 167. If a candle consists of 85% of carbon and 15% of hydro- gen, what weights of carbon dioxide and water will be formed when 25 grams of the candle burns? Ans. 77.91 grams CO2. 33.51 grams H2O. 168. What volume of carbon dioxide, measured at 750 mm. pressure and 20°C., will be formed when 17 grams of the candle, mentioned in the preceding question, is burned? Ans. 29.32 liters CO2. 31 169. If one liter of acetylene is burned, what volume of oxygen is necessary for the combustion and what volume of carbon dioxide will be formed? Ans. 2.5 liters oxygen. 2 liters carbon dioxide. 170. What weight of carbon dioxide would be obtained by burning 17 grams of carbon? Ans. 62.33 grams. 171. What volume of oxygen will unite with 730 cc. of carbon monoxide to form carbon dioxide, and what will be the volume of the carbon dioxide produced? Ans. 365 cc. oxygen. 730 cc. carbon dioxide. 172. What weight of carbon monoxide wUI result on heating 70 grams of oxalic acid, H2C2O4, with concentrated sulphuric acid? Ans. 21.77 grams CO. 173. What volume of water gas Will be produced upon decom- posing one ton of steam with hot coke? Ans. 2256.2 cubic meters. 174. If 100 grams of oxalic acid is heated with concentrated sulphuric acid and the gases are passed through a solution of sodium hydroxide, what volume of carbon monoxide and what weight of sodium carbonate will result? Ans. 24.86 liters CO. 117.86 grams NajCOs. 175. With anthracite coal (assumed to be pure carbon), at $5.00 per ton, what will be the cost of the carbon necessary to produce 1000 cubic feet of water-gas, assuming that the reaction is as represented by the equation C + H2O = CO + H2? Ans. $0,042. 176. How much acetic acid, C2II402, must be decomposed in order to obtain 10 Uters of marsh gas? Ans. 26.81 grams. 177. From 10 pounds of pure limestone how many liters of carbon dioxide could be obtained? Ans. 1015.57 liters. 178. If 13 liters of carbon dioxide is passed through a solution of caustic potash, how many grams of potassium hydroxide will be converted into potassium carbonate? Ans. 65.2 grams. 32 179. If 100 grams of sodium carbonate is treated with hydro- chloric acid, how many grams of salt, and how many liters of carbon dioxide (density referred to air = 1.52) will be formed .J* Ans. 110.27 grams NaCl. 21.1 liters COj. 180. If one cubic meter of carbon dioxide is absorbed by lime- water, what weight of calcium carbonate will be formed? Ans. 4470.37 grams CaCOg. 181. A steel cylinder of four cubic feet capacity is to be filled with carbon dioxide imder a pressure of 150 pounds to the square inch. What weight of marble and hydrogen chloride would be needed to produce the necessary amount of gas? Ans. 5.06 kilograms CaCOs. 3.69 kilograms HCl. 182. What per cent, of sulphur is contained in pure iron pyrites, FeS2? Ans. 53.42. 183. What volume of sulphur dioxide would result from heat- ing in the air one ton of pure iron pyrites, assuming that all of the sulphur in the pyrites is converted to sulphur dioxide? Ans. 338.79 cubic meters. 184. What volume of hydrogen sulphide will be formed upon treating 40 grams of ferrous sulphide, FeS, with hydrochloric acid? Ads. 10.17 liters HaS. 185. What volume and what weight of sulphur dioxide will be formed upon burning one liter of hydrogen sulphide? Ans. 1 liter SO2. 2.86 grams SO2. 186. If hydrogen sulphide and sulphur dioxide could be caused to react completely in the manner expressed by the equation SO2 -f 2 H2S = 3 S -H 2 H2O, what volume of sulphur dioxide and of hydrogen sulphide would be needed to liberate 96 grams of sulphur? Ans. 22.4 liters SO2. 44.8 liters HjS. 187. If a solution containing 50 grams of lead nitrate, Pb (N03)2, is precipitated by hydrogen sulphide, what will be the weight of the precipitate, PbS? Ans. 36.1 grams. 33 188. If a solution containing 50 grams of copper sulphate, CUSO4, is precipitated by hydrogen sulphide, what will be the weight of the precipitate, CuS? Ans. 29.96 grams. 189. How much sulphuric acid could be produced from the sulphur dioxide arising from the combustion of one ton of sulphur? Ans. 3.06 tons. 190. How much sulphuric acid could be produced from the sulphur dioxide arising from the combustion of one ton of pure iron pyrites? Ans. 3268.6 pounds. 191. If 100 cc. of a solution of barium chloride that contains 20 grams of the salt in one liter is precipitated by sulphuric acid, what weight of barium sulphate will be formed? Ans. 2.24 grams. 192. An ore contains 62.38 per cent, of arsenopyrite, FeAsS. What weight of arsenic could be obtained by heating 500 pounds of the ore? Ans. 65.17 kilograms. 193. What volume of arsine, AsHa, will result when 150 milli- grams of arsenic trioxide, AsjOs, is acted upon by nascent hydro- gen? Ans. 33.92 cc. 194. What weight of arsenic would be obtained by reducing 157 grams of arsenic trioxide with charcoal? Ans. 118.939 grams. 195. What is the per cent, of boron in crystallized borax, Na2B407 • IOH2O? Ans. 11.51 per cent. 196. What is the per cent, of silicon in quartz? Ans. 47.02 per cent. 197. What weight of silicon tetrafluoride, SiF4, could be obtained by treating 430 grams of silica, SiOz, with hydrofluoric acid? Ans. 743.24 grams. 198. If 275 grams of silica is fused with an excess of potassium carbonate, what weight of potassium silicate, K2Si03, will result? Ans. 704.34 grams. 199. From 1500 pounds of salt how many kilograms of sodium carbonate can be obtained by the Leblanc process? How much charcoal and how much limestone will be required? Ans. NaaCOs-lOHaO = 1666.18 kilograms. CaCOs required = 582.63 kilograms. Carbon required = 139.69 kilograms. 200. What weight of calcium sulphide will be produced in the manufacture of one ton of dry sodium carbonate by the Leblanc process? Ans. 1360.22 povmds. 201. What weights of salt, ammonia, and carbon dioxide will be necessary to produce one ton of sodium bicarbonate by the Solvay process? Ans. 1391.89 pounds NaCl. 405.29 poimds NH3. 1046.89 pounds CO2. 202. What weight of anhydrous sodium carbonate will result from heating 500 grams of sodium bicarbonate? Ans. 315.55 grams. 203. What weight of washing powder ("sal soda") would be needed to furnish 125 grams of anhydrous sodium carbonate? Ans. 337.25 grams. 204. What is the per cent, of sodium in Glauber's salt? Ans. 14.30. 205. What would be the volume, under standard conditions, of the gases evolved from a mixture of 10 grams of potassium nitrate with such amounts of carbon and sulphur as are required by the equation: 2KNO3 +3C+S = 3C02+N2+K2S? Ans. CO2, 3.320 liters. Ans. N2, 1.104 liters. ToUiI 4.424 liters. 206. How many pounds of quicklime and how many cubic meters of carbon dioxide would be formed by heating 5 tons of Umestone? Ans. CaO, 5604.4 pounds. CO2, 1015.5 cubic meters. 207. How many pounds of water would be needed to slake 15 pounds of quicklime? Ans. 4.81 pounds. 208. In the changing of 500 pounds of calcium hydrate, in mortar, to calcium carbonate, how many pounds of water are pro- duced? Ans. 121.53 pounds. 209. How much Plaster of Paris, (CaS04)2 • H2O, will result from heating 100 kilograms of gypsum? Ans. 84.3 kilograms. 35 210. How much quicklime and how much coke are needed for the production of 100 pounds of calcium carbide? Ans. 87.52 pounds CaO. 56.16 pounds carbon. 211. What volume of acetylene will be formed when 100 pounds of calcium carbide is treated with water? Ans. 15.856 cubic meters. 212. How many pounds of calcium carbide will be necessary to produce 1300 liters of acetylene when the temperature is 21°C. and the pressure is 745 mm.? Ans. 7.47 pounds. 213. How many liters of acetylene can be obtained from 50 grams of calcium carbide which is 93% pure, if the gas be evolved at a temperature of 40°C. and a pressure of Ij^ atmospheres? Ans. 12.41 liters. 214. What per cent, of magnesium oxide is contained in crystaUized potassium magnesium sulphate, K2S04'MgS04'6 H2O? Ans. 10.018 per cent. 215. How many pounds of zinc may be obtained from a ton of an ore containing 17.3 per cent, of zinc carbonate? Ans. 180.4 pounds. 216. What weights of mercury and sulphm* dioxide could be obtained from one ton of an ore carrying 53.78 per cent, of cinna- bar? Ans. Hg, 927.0 pounds. SO2, 296.9 pounds. 217. What weight of aluminum oxide is contained in 100 pounds of potassium alum? Ans. 10.76 pounds. 218. What weight of aluminum oxide is contained in 100 lbs. of aluminum sulphate, Al2(S04)3? Ans. 29.84 lbs. 219. What weight of aluminum hydroxide will be produced when a solution containing 35 grams of potassium alum is pre- cipitated with ammonium hydroxide? Ans. 5.76 grams. 220. What per cent, of aluminum does alum contain? Ans. 6.6 per cent. 221. What weight of iron will result from the reaction of 5 kilograms of thermit; 2 Al -f FeaOs = AI2O3 -|- 2 Fe? Ans. 2.6 kilograms. 36 An ore contains 23.46 per cent, of stibnite, SbjSs. What is the per cent, of antimony in the ore? Ans. 16.756 per cent. 223. How much chrome alum could be made from 10 kilo- grams of chromite? Ans. 44.58 kilograms. 224. What weight of chrome yellow would be formed it a solu- tion contauiLng 430 grams of potassium chromate were precipitated with lead acetate? Ans. 714.4 grams. 225. What weight of potassium permanganate could be pre- pared from 10 kilograms of an ore containiag 62% of pyrolusite? Ans. 11.27 kilograms. 226. Potassium permanganate oxidizes a ferrous salt to a ferric salt thus: 2 KMn04 + 10 FeSOi + 8 H2SO4 = 5 Fe2 (804)3 + K2SO4 + 2 MnSOi + 8 H2O. How many grams of potassium permanganate would be needed to oxidize a solution that contains 15.19 grams of ferrous sulphate? Ans. 3.16 grams. 227. If a solution of potassium permanganate contains 1.58 grams of the salt in one liter, what weight of ferrous sulphate would 10 cc. of the solution oxidize to ferric sulphate? Ans. 75.9 milligrams. 228. How many tons of pure hematite would be needed for the production of 100 tons of iron in the blast furnace, assuming that 2.3% of the iron in the ore passes into the slag? Ans. 146.3 tons. 229. How much coke would be needed to reduce 50 tons of pure hematite, assuming that the reaction proceeds as follows : 2 FeaOs -f-3C = 4Fe-f3 CO2. Ans. 5.63 tons. 230. An ore contains 36.4 per cent, of "ruby copper," CU2O. With what weight of charcoal (carbon) must 10 tons of the ore be heated in order to reduce all of the CU2O to metallic copper? (CU2O + C = 2Cu + CO.) Ans. 610.05 pounds. 37 231. What weight of copper will be obtained ui the preceding? Ans. 6466.7 pounds. 232. A silver coin, containing 8 per cent, of copper, weighs 2.43 grams. If the coin be dissolved in nitric acid, how many grams of sodium chloride will be required to precipitate all of the silver as silver chloride? Ans. 1.21 grams. 233. In the preceding, what weight of iron will be required to reduce the silver chloride formed to metallic silver? Ans. .58 gram. What will be the weight of silver obtained? Ans. 2.235 grams. CALCULATION OF FORMULA FROM PERCENTAGE COMPOSITION AND DENSITY The formula of a compound of known percentage composition may be ascertained by dividing the percentage amount of each element by the atomic weight of that element. There will thus be obtained a series of numbers that are to each other as the numbers of atoms of the different elements in the compound. For example, oxalic acid has the following composition: Carbon 26.66 per cent. Hydrogen 2.24 per cent. Oxygen 71.1 per cent. Dividing each of these percentages by the atomic weight of the element concerned — C 26.66 H 2.24 O 71.1 12 = 2.22 1.008 = 2.22 16 = 4.44 These resulting numbers are to each other as 1 : 1 : 2. The simplest formula is, then CHO2. The true formula may be this or some multiple of it, as C2H2O4, or C3H3O6, etc. To know which is correct, the molecular weight of the compound must be ascer- tained. It sometimes happens that the above method gives fractional ratios between the atoms. For example, red lead has the following composition : Lead 90.65 per cent. Oxygen 9.35 per cent. 90.65 ^ 206.9 = .438 9.35 ^ 16 = .584 The ratio is here .438 : .584 or 1 : 1.33. In such a case we multiply by such a number as will clear the ratio of fractions. In the example just given, where the ratio is 1:1.33 both numbers are multiplied by three, and we thus obtain the ratio 3:4. The formula of red lead is therefore Pb304. 234. What is the simplest formula of a substance that con- sists of oxygen, 88.809 per cfent., and hydrogen, 11.191 per cent? Ans. H2O, 235. Calculate the simplest formula of a mercuric oxide that contains 92.593 per cent, of mercury and 7.407 per cent, of oxygen. Ans. HgO. 236. What is the simplest formula of a substance consisling of calcium, 29.451 per cent., sulphur, 23.545 per cent., and oxygen 47.004 per cent? Ans. CaS04. 237. The percentage composition of a mineral is found to be: calcium, 40.06 per cent.; carbon, 11.99 per cent.; and oxygen, 47.95 per cent. What is its simplest formula? Ans. CaCOs. 238. Alcohol is found to have the following composition: C, 52.12 per cent.; O, 34.75 per cent.; H, 13.13 per cent. The density (referred to air) of alcohol vapor is 1.595. What is the formula of the substance? Ans. C2H6O. (Calculating the formula by the method explained on page 38, it will be found that the simplest formula for alcohol is C2H6O, but, as explained above, the true formula may be this or some multiple of it, as C^Hi202, CeHisOs, etc. To ascertain which of these formu- las is the true one, compute the molecular weight of the compound from the density of alcohol vapor (see (4) p. 27.) 1.595 X 28.96 = 46.19. The calculated molecular weights corresponding to the three possible formulas suggested above are — C2H6O = (2 X 12) + 6 X (1.008) + 16 = 46.048 CiHijOa = (4 X 12) + (12 X 1.008) + (2 X 16) = 92.096 CsHisOs = (6 X 12) + (18 X 1.008) + (3 X 16) = 138.144 The molecular weight computed from the vapor density, 46.19, agrees more closely with the first of Ihe calculated molecular weights than with any of the others. Consequsntly, C2H6O is accepted as the true formula of alcohol). 239. The percentage composition of acetic acid is carbon 39.98 per cent., hydrogen 6.72 per cent., and oxygen 53.30 per cent. What is the simplest formula that could be given lo the substance? Ans. CH2O. 40 240. It is found, however, that the density (air) of acetic acid vapor is 2.079. What then, is its true formula? Ans. C2H4O2. 241. What will be the formula of a hydrocarbon which con- tains twice as many atoms of hydrogen as of carbon, and the vapor of which has a density (air) of 1.947? Ans. C4H8. 242. What is the formula of a hydrocarbon which contains an equal number of hydrogen and carbon atoms, and the vapor of which has a density (air) of 2.712? Ans. CeHe. Formic acid has the composition: C, 26.08 per cent.; O, 69.54 per cent.; H, 4.38 per cent. The density (air) of its vapor is the same as that of alcohol: what is its formula? Ans. H2CO2. 244. Aldehyde has the following percentage composition: C, 54.50 per cent.; H, 9.16 per cent.; 0,-36.34 per cent. The density (air) of its vapor is 1.526. What is its formula? Ans. C2H4O. 245. Butyric acid has the same percentage composition as aldehyde, but the density (air) of its vapor is 3.052. What is its formula? Ans. C4H8O2. 246. A compound has the following percentage composition: carbon, 37.46 per cent.; hydrogen, 12.59 per cent.; oxygen, 49.95 per cent. One liter of its vapor weighs 1.4339 grams. What is its formula? Ans. CH4O. 247. A gas has the following composition: carbon, 27.272 per cent.; oxygen, 72.727 per cent. Its density (air) is 1.52. What is its formula? Ans. CO2. 248. A compound has the following percentage composition: oxygen, 76.17 per cent.; hydrogen, 1.6 per cent.; nitrogen, 22.23 per cent. One liter of its vapor weighs 2.817 grams. What is its molecular weight and formula? Ans. 63.018 and HNO3. 249. A hydrocarbon consists of carbon 93.703 per cent.; hydrogen, 6.296 per cent. The density (air) of its vapor is 4.456. What is its formula? Ans. CioHs. 41 250. A gas has the following composition: nitrogen, 30.45 per cent.; oxygen, 69.55 per cent. One liter of the gas weighs 2.058 grams. What is its molecular weight and formula? Ans. 46.01 and NO2. 251. A compound has the following percentage composition: H, 1.19 per cent.; O, 56.84 per cent.; -CI, 41.97 per cent. One liter of its vapor weighs 3.771 grams. What is its molecular weight and formula.? Ans. 84.458 and HCIO3. 252. A compound has the following composition : phosphorus, 2.22 per cent.; oxygen, 10.43 per cent.; chlorine, 69.35 per cent. The density (air) of its vapor is 5.295. What is its formula .'' Ans. POCI3. 253. A compound has the following percentage composition: I = 96.70 per cent.; C = 3.045 per cent.; H = .255 per cent. The density (air) of its vapor is 13.595. What is its formula? Ans. CHI3. 254. A compound has the following compositions: phos- phorus 22.57 per cent.; chlorine, 77.43 per cent. One liter of its vapor weighs 6.131 grams. Calculate its molecular weight and formula. Ans. 137.35 and PCI3. 255. At a temperature but little above its boiling point sulphur vapor is found to have a density of 6.675, while at 860° the density of the vapor is only 2.225. What conclusion would you draw in regard to the constitution of the sulphur molecule at these tempera- tures? Ans. Se and S2. CALCULATION OF AT0:MIC WEIGHT FROM SPECIFIC HEAT 256. The molecular weight of potassium chloride is 74.6. The per cent, of potassium in the compound is 52.479. The specific heat of potassium is 0.166. What is the atomic weight of the element? 257. The molecular weight of lead oxide, PbO, is 222.9. The per cent, of lead = 9'2. 821. Specific heat of lead = 0.031. What is its atomic weight? 258. A compound of hydrogen and sulphur has a molecular weight of 34. The per cent, of sulphur in the compound is 94.11. Specific heat of sulphur = 0.184. What is its atomic weight? 259. Analysis of uranium chloride shows the composition U = 62.713 per cent., CI = 37.287 per cent. The specific heat of metallic uranium is 0.027. What is the atomic weight of uranium, and what the formula of the chloride? Ans. 238.5 and UCU- Cornell University Library QD 42.D41 Problems in inorganic chemistry, 3 1924 004 177 881