Question

For a second order reaction in which both the reactants have equal initial concentration, the time taken for 20% completion of reaction is 500 second. What will be the time taken for 60% of the reaction?

• A. 500 sec
• B. 1000 sec
• C. 300 sec
• D. 1500 sec

Answer 1

Answer: (C)

300 sec

Answer 2

We know that $k=\frac{1}{t} \times\frac{x}{a\left(a-x\right)}$ [For a second order reaction] $Since\, x=\frac{20}{100}=0.2, a=1$ $k=\frac{1\times0.2}{500\times1\left(1-0.2\right)}=\frac{1}{500\times4}$ $Now, k=\frac{1}{t}\times\frac{0.6}{1\left(1-0.6\right)}$ $\therefore\, \frac{1}{500\times4}=\frac{1}{t}\times\frac{0.6}{0.4} \Rightarrow\, t=3000 seconds$