30 г                                                         V = ?

 2Na       +       2H2O     =    2NaOH     +    H2

n= 2 моль                                               n= 1 моль

М= 23 г/моль                                          Vm=22,4 л/моль

m= 46 г                                                  V = 22,4 л

30 г Na - X л Н2

46 г Na - 22,4 л Н2

V(H2) = 30 * 22,4 \ 46 = 14,6 л