## Edition 6 15.23

$\frac{d[R]}{dt}=-k[R]; \ln [R]=-kt + \ln [R]_{0}; t_{\frac{1}{2}}=\frac{0.693}{k}$

Christine Chen 1H
Posts: 64
Joined: Fri Sep 28, 2018 12:18 am

### Edition 6 15.23

For part c, isn't it second-order and not first-order? Bc 2A --> B + C ; k = [A]^2 ?
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Anand Narayan 1G
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

### Re: Edition 6 15.23

It is a second order reaction, Im pretty sure that's a typo for that problem as in 15.39 they mention the same equation (2A --> B + C) and call it a second-order reaction

timothy_ho_4B
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

### Re: Edition 6 15.23

Actually, I believe that the coefficients don't necessarily determine the order of the entire reaction because it ultimately boils down to the experimental analysis of initial rates to find the order (unless it is already given). The coefficient rule applies to elementary steps but not if the question is regarding the entire reaction. So the reaction can be 2A --> B + C can be zero, first, or second order, but we can't really tell unless we have experimental values.