JEE Mains · Chemistry · STD 12 - 3. Chemical kinetics
If \(75 \%\) of a first order reaction was completed in \(90\) minutes, \(60 \%\) of the same reaction would be completed in approximately (in minutes).......... (Take: \(\log 2=0.30 ; \log 2.5=0.40)\)
- A \(65\)
- B \(75\)
- C \(70\)
- D \(60\)
Answer & Solution
Correct Answer
(D) \(60\)
Step-by-step Solution
Detailed explanation
\(t _{0.75}=2 \times \frac{\ln 2}{ k }=90\) \(k =\frac{\ln 2}{45} min ^{-1}\) \(kt =\ln \frac{1}{1-0.6}=\ln 2.5\) \(\frac{\ln 2}{45} \times t=\ln 2.5\) \(t=45 \times \frac{\log 2.5}{\log 2}=45 \times \frac{0.4}{0.3}=60 min\)
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