40 г                                     Х г   Zn        +      2HCl      =       ZnCl2       +       H2n = 1 моль                          n = 1 мольMr = 65 г/моль                   Mr = 135 г/мольm = 65 г                             m = 135 г40 г Zn    -    Х г ZnCl265 г Zn   -    135 г ZnCl2m(ZnCl2) = 40 * 135 / 65 = 83 г