Zn + 2HCl = ZnCl2 + 2 H | H giv. : H req. :: HCl giv. : HCl req. 73 2 | 2 : 12 :: 73 x x 12 | 2x=876 x=438 Ans. 438 g. HCl. Solve:-- (1) How much HCl is needed to produce 100 g. H? (2) How much H in 10 g. HCl? (3) How much ZnCl2 is formed by using 50 g. HCl? The question is now between HCl and ZnCl2. Zn + 2HC1 = ZnCl2 + 2H 73 136 | Arrange the proportion, and solve. 50 x Suppose we have generated H by using H2S04: the equation is Zn + H2S04 = ZnSO4 + 2 H. There is the same relation as before between the quantities of Zn and of H, but the H2S04 and ZnS04 are different. How much H2SO4 is needed to generate 12 g. H? Zn + H2SO4 = ZnS04 + 2 H 98 2 | Make the proportion, and solve x 12 Solve:-- (1) How much H in 200 g. H2S04? (2) How much ZnS04 is produced from 200 g. H2S04? (3) How much H2S04 is needed for 7 1/2 g H? (4) How much Zn will 40 g. H2SO4 combine with? (5) How much Fe will 40 g. H2SO4 combine with? (6) How much H can be obtained by using 75 g Fe? These principles apply to all reactions. Suppose, for example, we wish to get l0 g. of O: how much KClO3 will it be necessary to use? The reaction is:-- KClO3 = KCl + O3 | 48 : 10 :: 122.5 : x 122.5 48 | x 10 | Ans. 25.5+ g. KClO3. The pupil should be required to make up problems of his own, using various reactions, and to solve them. CHAPTER X. CARBON. Examine graphite, anthracite coal, bituminous coal, cannel coal, wood, gas carbon, coke. 40. Preparation of C. Experiment 26.--Hold a porcelain dish or a plate in the flame of a candle, or of a Bunsen burner with the openings at the bottom closed. After a minute examine the deposit. It is carbon, i.e. lamp- black or soot, which is a constituent of gas, or of the candle. Open the valve at the base of the Bunsen burner, and hold the deposit in the flame. Does the C gradually disappear? If so, it has been burned to CO2. C + 2 O = CO2. Is C a combustible element? Experiment 27.--Ignite a splinter, and observe the combustion and the smoke, if any. Try to collect some C in the same way as before. With plenty of O and high enough temperature, all the C is burned to CO2, whether in gas, candle, or wood. CO2 is an invisible gas. The porcelain, when held in the flame, cools the C below the point at which it burns, called the kindling-point, and hence it is deposited. The greater part of smoke is unburned carbon.