Х моль                                               5 г

  CO2       +          Ca(OH)2       =       CaCO3      +    H2O

n = 1 моль                                         n = 1 моль

                                                          Mr = 100 г/моль

                                                          m = 100 г

Х моль СО2   -    5 г СаСО3

1 моль СО2   -   100 г СаСО3

n(CO2) = 5/100 = 0,005 моль