The Student Room Group

Initial rate chapter 18 A2

The experiment was repeated at the same temperature and with the same initial concentration of B but with a different initial concentration of A.

The new initial rate was 1.7 times greater than in the original experiment.
Calculate the new initial concentration of A.
(edited 1 month ago)
Reply 1
Original post by salina1147
The experiment was repeated at the same temperature and with the same initial concentration of B but with a different initial concentration of A.
The new initial rate was 1.7 times greater than in the original experiment.
Calculate the new initial concentration of A.

Without the rate equation, I don't think we can help you.
Original post by salina1147
The experiment was repeated at the same temperature and with the same initial concentration of B but with a different initial concentration of A.
The new initial rate was 1.7 times greater than in the original experiment.
Calculate the new initial concentration of A.

Even with the (limited) information given, I think it is still possible to give you pointers as to how to proceed.

Since this is an A level problem, the order of reaction with respect to any reagent will either be 0, 1 or 2. In this case, the order with respect to A cannot be 0 as that would suggest that increasing its concentration without changing any other conditions would have no effect on the rate.

If the reaction is first order with respect to A, then we can say

the factor by which the rate increases = the factor by which [A] increases

If instead it is second order with respect to A, we can say

the factor by which the rate increases = (the factor by which [A] increases)^2

I can show this mathematically, which I'll do in a spoiler as it may help you to understand the principle.


Mathsy nonsense

Original post by TypicalNerd
Even with the (limited) information given, I think it is still possible to give you pointers as to how to proceed.
Since this is an A level problem, the order of reaction with respect to any reagent will either be 0, 1 or 2. In this case, the order with respect to A cannot be 0 as that would suggest that increasing its concentration without changing any other conditions would have no effect on the rate.
If the reaction is first order with respect to A, then we can say
the factor by which the rate increases = the factor by which [A] increases
If instead it is second order with respect to A, we can say
the factor by which the rate increases = (the factor by which [A] increases)^2
I can show this mathematically, which I'll do in a spoiler as it may help you to understand the principle.

Mathsy nonsense


Note that TSR has decided to butcher the formatting in the spoiler every time I’ve tried to include the concentration of B
(edited 1 month ago)

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