Finding order wrt reactant HELP! Watch

Yatayyat
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Link to Q: https://imgur.com/UYUMbGj

It's part c i) that I'm stuck on.

I have already attempted and answered the previous parts of the Q which were...

part a) It's the exponent value for the concentration term

part b) both reactants A and B seem to be first order so finding the overall order is to add up the individual orders which turns out to be 2nd order for the overall order of the reaction

In c i) Not really sure what to do. It mentions that the initial rate gets increased by 9x or increased by 3^2 times when reactant A is tripled and reactant B halved

I would have thought that rate is proportional to [A] squared hence indicating a 2nd order with reactant A, but doesn't [B] change i.e. get halved to affect the initial rate.

Any help would be great! Thanks!
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Pigster
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How do 2nd, 1st and 0th orders affect rate?
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Yatayyat
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(Original post by Pigster)
How do 2nd, 1st and 0th orders affect rate?
Well if I had a reactant called X then:

If [X] changes but the rate remains unchanged (same), the order of reaction wrt [X] is 0

Order of reaction wrt [X] is 1 if rate is directly proportional to [X], so when it is something like [X] is quadrupled then rate should also quadruple.

Order of reaction wrt [X] is 2 if rate is directly proportional to [X] squared, so when [X] triples then rate would increase by 9x more.

I think I just realised my mistake, order wrt [B] has to be 0 because although [B] reduces to half the amount rate seems not at all affected or else rate wouldn't increase by 9x.

So order wrt [A] is 2
order wrt [B] is 0
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Pigster
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(Original post by Yatayyat)
So order wrt [A] is 2
order wrt [B] is 0
I'll just confirm what you already know to be true.
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Yatayyat
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(Original post by Pigster)
I'll just confirm what you already know to be true.
Thank you for doing so much appreciated!
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