A) 1980s
B) 25905s
C) 9905 s
D) 4455 s
Correct Answer: A
Solution :
Key Idea: Use the following equation to find the time. \[t=\frac{2.303}{k}\log \left[ \frac{{{A}_{0}}}{A} \right]\] where, k = rate constant \[=7\times {{10}^{-4}}s\] \[[{{A}_{0}}]=\] initial concentration = 1 \[[A]=1/4\] (concentration at time 0 \[\therefore \] \[t=\frac{2.303}{7\times {{10}^{-4}}}\log \left[ \frac{1}{1/4} \right]\] \[=0.329\times {{10}^{4}}\log 4\] \[=0.329\times {{10}^{4}}\times 0.6020\] = 1980 s
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