How are 0.50 mol` Na_(2)CO_(3)` and 0.50 M `Na_(2)CO_(3)` different?

Explanation

Molar mass of `Na_2CO_3 = (2 xx 23) + 12 + (3 xx 16) = 106`
0.50 mol `Na_2CO_3` means `0.50 xx 10^6 = 53` g of `Na_2CO_3`. It refers to the mass only.
`0.50 M Na_2CO_3` means 0.50 mol, i.e., 53 g of `Na_2CO_3` are present in 1 litre of the solution. Thus, it refers to the strength of the solution.