Question

How are $0.50m$ ${Na}_2{CO}_3$ and $0.50M$ ${Na}_2{CO}_3$ different?

Answer 1

The molar mass of sodium carbonate is $2\left(23\right)+12+3\left(16\right)=106$ g/mol.
$0.50$ moles of sodium carbonate corresponds to $0.5$ mol $\times 106$ g/mol $=53$ g of $N{a}_{2}C{O}_3$.
In $0.50m$ sodium carbonate solution, $0.5$ mol of sodium carbonate is present in $1000$ g of water.
In $0.50M$ sodium carbonate solution, $0.5$ moles of sodium carbonate is present in $1$ L of solution.