Em tham khảo nha :
\(\begin{array}{l}
1)\\
2{H_2} + {O_2} \to 2{H_2}O\\
{n_{{H_2}O}} = \dfrac{m}{M} = \dfrac{{45}}{{18}} = 2,5mol\\
{n_{{H_2}}} = {n_{{H_2}O}} = 2,5mol\\
{V_{{H_2}}} = n \times 22,4 = 2,5 \times 22,4 = 56l\\
2)\\
{m_{NaCl}} = 40g\\
{V_{NaCl}} = 160ml\\
{n_{NaCl}} = \dfrac{m}{M} = \dfrac{{40}}{{58,5}} = \frac{{80}}{{117}}(mol)\\
{C_M} = \dfrac{n}{V} = 4,27M\\
3)\\
C{O_2} + Ca{(OH)_2} \to CaC{O_3} + {H_2}O\\
{n_{C{O_2}}} = \dfrac{V}{{22,4}} = \dfrac{{4,48}}{{22,4}} = 0,2mol\\
{n_{Ca{{(OH)}_2}}} = {n_{C{O_2}}} = 0,2mol\\
{C_{{M_{Ca{{(OH)}_2}}}}} = \dfrac{n}{V} = \dfrac{{0,2}}{{0,4}} = 0,5M
\end{array}\)