Em tham khảo nha :
\(\begin{array}{l}
a)\\
{n_{{H_2}S{O_4}}} = 0,1mol\\
{V_{{H_2}S{O_4}}} = 250ml = 0,25l\\
{C_{{M_{{H_2}S{O_4}}}}} = \dfrac{n}{V} = \dfrac{{0,1}}{{0,25}} = 0,4M\\
b)\\
{n_{NaOH}} = \dfrac{m}{M} = \dfrac{{20}}{{40}} = 0,5mol\\
{V_{NaOH}} = 400ml = 0,4l\\
{C_{{M_{NaOH}}}} = \dfrac{{0,5}}{{0,4}} = 1,25M
\end{array}\)