Em tham khảo nha :

\(\begin{array}{l}
3)\\
tt:\\
{m_{Mg}} = 24g\\
{m_{{\rm{dd}}HCl}} = 200g\\
a)\\
Mg + 2HCl \to MgC{l_2} + {H_2}\\
{n_{Mg}} = \dfrac{{2,4}}{{24}} = 0,1mol\\
{n_{HCl}} = 2{n_{Mg}} = 0,2mol\\
{m_{HCl}} = 0,2 \times 36,5 = 7,3g\\
C{\% _{HCl}} = \dfrac{{7,3}}{{200}} \times 100\%  = 3,65\% \\
b)\\
{n_{MgC{l_2}}} = {n_{Mg}} = 0,1mol\\
{m_{MgC{l_2}}} = 0,1 \times 95 = 9,5g\\
c)\\
{n_{{H_2}}} = {n_{Mg}} = 0,1mol\\
{V_{{H_2}}} = 0,1 \times 22,4 = 2,24l\\
4)\\
tt:\\
{m_{Zn}} = 3,25g\\
{V_{HCl}} = 200ml = 0,2l\\
a)\\
Zn + 2HCl \to ZnC{l_2} + {H_2}\\
{n_{Zn}} = \dfrac{{3,25}}{{65}} = 0,05mol\\
{n_{HCl}} = 2{n_{Zn}} = 0,1mol\\
{C_{{M_{HCl}}}} = \dfrac{{0,1}}{{0,2}} = 0,5M\\
b)\\
{n_{ZnC{l_2}}} = {n_{Zn}} = 0,05mol\\
{m_{ZnC{l_2}}} = 0,05 \times 136 = 6,8g\\
c)\\
{n_{{H_2}}} = {n_{Zn}} = 0,05mol\\
{V_{{H_2}}} = 0,05 \times 22,4 = 1,12l
\end{array}\)