To avoid error in solving similar problems, the best plan is as follows:—
Zn + 2HCl = ZnCl2 + 2 H | 65:5::2:x 65 2 | 65 x = 10 5 x | x = 10/65 = 2/13 Ans. 2/13 g.
The equation should first be written; next, the atomic or molecular weights which you wish to use, and only those, to avoid confusion; then, on the third line, the quantity of the substance to be used, with underneath the substance wanted. The example above will best how this. This plan will prevent the possibility of error. The proportion will then be:—
a given : a required :: b given : b required.
How much Zn is required to produce 30 g. H?
Zn + 2HCl = ZnCl2 + 2H | 2:30::65:x 65 2 | 2x = 1950 x 30 | x = 975 Ans. 975 g. Zn.
Solve:—
(1) How much Zn is necessary for 14 g. H?
(2) How many pounds of Zn are necessary for 3 pounds of H?
(3) How many grams of H from 17 g. of Zn?