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InterviewSolution
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In a first order reaction, `75%` of the reactants disappeared in `1.386 hr`. What is the rate constant ?A. `3.6 xx 10^(-3)s^(-1)`B. `7.2 xx 10^(-3)s^(-1)`C. `2.7 xx 10^(-4)s^(-1)`D. `1.8 xx 10^(-3)s^(-1)` |
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Answer» Correct Answer - C Let original amount `N_(0) = 100` Since, disappeared amount `= 75%` `:.` left amount, `N = 100 - 75 = 25` `:.` Since, `(N_(0))/(N) = 2^(n)` where `n =` no. of hlaf lives or, `(100)/(25) = 2^(n)` or, `2^(2) = 2^(2)`, here `n = 2` `because` Total time `= n xx t_(1//2)` `1.386` hours `= 2 xx t_(1//2)`, `t_(1//2) = 0.693` hours `= 2494.8 sec`. `k = (0.693)/(2494.8) = 2.7 xx 10^(-4) sec^(-1)` |
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