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# order of reaction watch

1. Why is order with respect to [H+] =1? I can get the first two but i don't know how to calculate for H+. I need help on part (iv) too Any help? Thanks
2. (Original post by Snowie9)
Why is order with respect to [H+] =1? I can get the first two but i don't know how to calculate for H+. Any help? Thanks
Compare 3 and 4, the concentration of aldehyde drops by 20% so you expect the overall rate to drop accordingly (from 2.00 to 1.60)

The only other change is in [H+], which doubles and the actual rate is infact 3.20, twice the rate we would expect based on only worrying about the change in aldehyde concentration, from that we can conclude that the doubled acid concentration must lead to a doubling in the rate.

With rate law questions, once you think you have worked out the order for each reagent you can always check!

The rate law we've come up with here is

rate=k [alcohol][aldehyde][H+]

now you can use the first row data to calculate a value of k for this reaction.

You can use that value of k to check that the concentrations in rows 2,3 and 4 do actually give the right rate from the table, if they do, you have the right answer! If not then you know you need to look again

You can also use your rate law in the same way to answer part (iv)
3. (Original post by MexicanKeith)
Compare 3 and 4, the concentration of aldehyde drops by 20% so you expect the overall rate to drop accordingly (from 2.00 to 1.60)

The only other change is in [H+], which doubles and the actual rate is infact 3.20, twice the rate we would expect based on only worrying about the change in aldehyde concentration, from that we can conclude that the doubled acid concentration must lead to a doubling in the rate.

With rate law questions, once you think you have worked out the order for each reagent you can always check!

The rate law we've come up with here is

rate=k [alcohol][aldehyde][H+]

now you can use the first row data to calculate a value of k for this reaction.

You can use that value of k to check that the concentrations in rows 2,3 and 4 do actually give the right rate from the table, if they do, you have the right answer! If not then you know you need to look again

You can also use your rate law in the same way to answer part (iv)
Thanks so much for your explanation.

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