13 г                                                                   Х л

    Zn         +         2HCl        =       ZnCl2      +    H2

n = 1 моль                                                       n = 1 моль

Mr = 63 г/моль                                                Vm = 22,4 л/моль

m = 63 г                                                             V = 22,4 л

13 г Zn    -     Х л Н2

63 г Zn    -    22,4 л Н2

V(H2) = 13 * 22,4 / 63 = 4,6 л