0,3 моль                                                   V=?

 2СH3COOH  +  Mg =  (CH3COO)2Mg    +  H2

n= 2 моль                                                    n= 1 моль

                                                                    Vm = 22,4 л/ моль

                                                                    V = 22,4 л

0,3 моль СН3СООН    -    Х л Н2

2 моль  СН3СООН    -     22,4 л Н2

V(H2) = 0,3 * 22,4 / 2 = 3,36 л