## 7B.3 Determining the order of a reaction

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

Ryan 1K
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### 7B.3 Determining the order of a reaction

For part c of 7B.3, I know that it says the reaction is first-order, but I thought that if there are two molecules in the reactants, it is a second-order reaction. Is it based on the notation (2A vs A+A) that tells us that it's not a second-order reaction?

Ipsita Srinivas 1K
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### Re: 7B.3 Determining the order of a reaction

The equation is bimolecular, but a first order reaction. The notation doesn't determine the order of the reaction For example, in example 7B.1, the equation is first-order in N2O5, despite there being two molecules. The notation is important when determining the rate of a multi-step reaction, but not it's order.
Equation: 2 N2O5(g) ---> 4 NO2(g) 1 O2(g)

Ryan 1K
Posts: 101
Joined: Fri Aug 09, 2019 12:15 am

### Re: 7B.3 Determining the order of a reaction

I thought molecularity and order went together? If not, what is the purpose of molecularity if not to go along with the order of a reaction?