Question
For a reaction $$R \to P,$$ the concentration of a reactant changes from $$0.05\,M$$ to $$0.04\,M$$ in 30 minutes. What will be the average rate of reaction in minutes?
A.
\[4\times {{10}^{-4}}\,M\,{{\min }^{-1}}\]
B.
\[8\times {{10}^{-4}}\,M\,{{\min }^{-1}}\]
C.
\[3.3\times {{10}^{-4}}\,M\,{{\min }^{-1}}\]
D.
\[2.2\times {{10}^{-4}}M\,{{\min }^{-1}}\]
Answer :
\[3.3\times {{10}^{-4}}\,M\,{{\min }^{-1}}\]
Solution :
\[\begin{align}
& \text{Average rate} \\
& =-\frac{\Delta \left[ R \right]}{\Delta t} \\
& =\frac{\left( {{\left[ R \right]}_{2}}-{{\left[ R \right]}_{1}} \right)}{{{t}_{2}}-{{t}_{1}}} \\
& =-\frac{\left( 0.04-0.05 \right)}{30} \\
& =\frac{0.01}{30} \\
& =3.3\times {{10}^{-4}}M\,{{\min }^{-1}} \\
\end{align}\]