# Consider the statement: Solid Mg added to 2M HCl. In the first 10 seconds,the temperature of container increased by $1^0C$ and 20ml of $H_2$ was produced. Determine rate of reaction.

$\begin{array}{1 1} 1\;ml \;lH_2/s \\ 2 \;ml\;H_2/s \\ 3 ml\;HCl /s \\ 0.05\;mol \;HCl /s\end{array}$

$Mg+2HCl\rightarrow MgCl_2+H_2$
Rate can be determine with respect to any reactant or product
So $R=\large\frac{d[H_2]}{dt}$
So rate=$\large\frac{20ml}{10}\frac{H_2}{sec}$
$\Rightarrow 2ml$ of $H_2$ per sec.
Hence (b) is the correct answer.