Question

calculate the mass of Na2Co3 which will have the same number of molecules as contained in 123g of MgSo4.7H2o

Answer 1

1 molecule of MgSO4.7H2O = 246g
123g MgSO4.7H2O = 1/2 molecule

1 molecule of Na2CO3 = 106g
1/2 molecule of Na2CO3 = 53 g

so, 53g Na2CO3 will have same number of molecules as 123g of MgSO4.7H2O