Rate constant from rate-concentration graph

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Why can't you obtain the rate constant from the gradient of a rate-concentration curve of a second-order reaction but you can via the gradient of a rate-concentration curve of a first-order reaction? I know that for the second order reaction the rate constant would change although I'm not sure how this makes the method wrong assuming the rate constant can change 🙂

Does the value of the rate constant have to be constant? 😂

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(Original post by Freedom physics)
Why can't you obtain the rate constant from the gradient of a rate-concentration curve of a second-order reaction but you can via the gradient of a rate-concentration curve of a first-order reaction? I know that for the second order reaction the rate constant would change although I'm not sure how this makes the method wrong assuming the rate constant can change 🙂

Does the value of the rate constant have to be constant? 😂

The rate constant is errr constant. It only changes with temperature.

Rate = k[A]^x

The second order reaction gives a curve.

Rate = k[A]²

You can plug in values of rate at any given concentration to find the rate constant.

The first order graph is a straight line. Once again simply plug in values to find 'k'.

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Freedom physics

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So why do you need to plot a graph of rate against concentration squared in order to find k for a second order reaction? Is it just because tangents are unreliable? 😄

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