## Order of Reactions

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

Cole Woulbroun 1J
Posts: 56
Joined: Thu Jul 25, 2019 12:16 am

### Order of Reactions

What determines whether a reaction is zero, first, or second order? I would assume that it would be molar ratios but I've seen exceptions to this so I was wondering what the explanation is.

Kaylee Sepulveda 4G
Posts: 100
Joined: Thu Jul 11, 2019 12:16 am

### Re: Order of Reactions

The order of reaction can be found experimentally by changing the concentration of reactants and observing the change in the rate of reaction. For example, if doubling the concentration of a reactant doubles the rate of reaction, the reaction is a first-order reaction for that reactant.

Esha Chawla 2E
Posts: 108
Joined: Thu Jul 25, 2019 12:17 am

### Re: Order of Reactions

Cole Woulbroun 1J wrote:What determines whether a reaction is zero, first, or second order? I would assume that it would be molar ratios but I've seen exceptions to this so I was wondering what the explanation is.

To determine if the reaction is zeroth order, plot the concentration over time. If this results in a line, the reaction is zeroth order. If the reaction is first order, plot the ln(concentration) over time. If this results in a line, the reaction is first order. If the reaction is second order, plot the 1/(concentration) over time. If this results in a line, the reaction is second order.

Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

### Re: Order of Reactions

the order is the dependence on the concentration of reactants. This typically corresponds to the exponent value. to find the order of a reaction, you simply add all the exponents of the reactants.

Juliana Chopelas 1A
Posts: 50
Joined: Sat Aug 24, 2019 12:16 am

### Re: Order of Reactions

Reaction order is dependent upon the concentrations of the reactions v time. If you are given a set of data, you can solve for n and m (the exponents for each reactant) by comparing two different trials that have the same concentrations for one reactant and different concentrations for the other to get the order. You can also solve the reaction order by looking at graphs. For a zero order, the graph is (A) v time and the graph would be linear if it is zero order. For first order the graph is ln(A) v time and the graph would appear linear if it is first order. And for second order the graph is 1/(A) v time and the graph would appear linear as well if it is second order.