# AS Chemistry question

https://www.quora.com/profile/Bravewarrior/p-146675165
Here is the question. I am stuck on 3aiii where it says suggest a possible value for the activation energy of the catalysed forward reaction. The answer is +1 to +249kJ per mole. Can someone please explain how? Thanks!

Edit: can someone also help me with part iv which is the last part of the question? For that one the answer is 342kJ per mole. Thank you!
(edited 4 months ago)
Original post by pigeonwarrior
https://www.quora.com/profile/Bravewarrior/p-146675165
Here is the question. I am stuck on 3aiii where it says suggest a possible value for the activation energy of the catalysed forward reaction. The answer is +1 to +249kJ per mole. Can someone please explain how? Thanks!

Edit: can someone also help me with part iv which is the last part of the question? For that one the answer is 342kJ per mole. Thank you!

A catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy. The activation energy of the uncatalysed reaction is +250 kJ mol-1. So the activation energy of the catalysed reaction must be less than that, and because energy is needed to be supplied in order to break bonds, the activation energy must be positive (greater than 0).

For part vi) you're going to want to do something with the Ea for the forward reaction, and the ΔH value for the forward reaction. Hint: as you're looking at the reverse reaction, you'll want to "reverse" the -92 kJ mol-1
Original post by bl0bf1sh
A catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy. The activation energy of the uncatalysed reaction is +250 kJ mol-1. So the activation energy of the catalysed reaction must be less than that, and because energy is needed to be supplied in order to break bonds, the activation energy must be positive (greater than 0).

For part vi) you're going to want to do something with the Ea for the forward reaction, and the ΔH value for the forward reaction. Hint: as you're looking at the reverse reaction, you'll want to "reverse" the -92 kJ mol-1

Thank you so much!! 🙂