26г                                                        V =?

     Na2CO3      +    2 HCl    =   2 NaCl    +   CO2   + H2O

 n = 1 моль                                              n = 1 моль

М = 106 г/моль                                       Vm= 22,4 л/моль

m = 106 г                                                V = 22,4 л

26 г Na2CO3      -    Х л СО2

106 г Na2CO3   -   22,4 л СО2

V(CO2) = 26 * 22,4 / 106 = 5,5 г