delta H and catalyst

[prsndwg]

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delta H is -75 and the activation energy is 40kj. a catalyst lowers the forward reaction acitvation energy by 15. what is the activation energy of reverse?


60?



one more:

2NO + Cl2 --> 2NOCl gases

doubling Cl, doubles the rate of the reaction. doubling the concentration of both reactants increases the rate of reaction by 8. What is the order of each reactant?

 

[hausee]

 

[hausee]

delta H is -75 and the activation energy is 40kj. a catalyst lowers the forward reaction acitvation energy by 15. what is the activation energy of reverse?


60?



one more:

2NO + Cl2 --> 2NOCl gases

doubling Cl, doubles the rate of the reaction. doubling the concentration of both reactants increases the rate of reaction by 8. What is the order of each reactant?

double cl2 and RXn double so Cl order is one. if double both, since double cl2 double RXn, so double NO will be like 4xRate(order 2)

Rate=k[Cl2]*[NO]^2

 

[prsndwg]

double cl2 and RXn double so Cl order is one. if double both, since double cl2 double RXn, so double NO will be like 4xRate(order 2)

Rate=k[Cl2]*[NO]^2

i got the other one, thanks, can you walk me through this one please? i am a lil confused

 

[Moabmad]

i got the other one, thanks, can you walk me through this one please? i am a lil confused

Double Cl = 2X Rate - therefore (order 1)

Double both Cl and NO = 8X Rate.....

Take into account of the effect of Cl which 2X the rate. Therefore the effect of doubling NO = 4X the rate. (2X from CL, 4X from NO = 8X overall)

Therefore doubling NO = 4X Rate (Order 2)

rate = k*[Cl]*[NO]^2

 

[UndergradGuy7]

if rate = K[Cl]^x * [NO]^y we need to know the exponents x and y.

What the problem tells us is that if we double the concentration of say [Cl] the rate will double. This is only possible is the exponent of Cl is 1. Check it with numbers. If the original concentration is 1M then (1)^1 = 1 If we double the concentration to 2M we get (2)^1 so a double in the rate. If the exponent was ^2 we would get (2)^2 = 4 which causes the rate to increase 4 times.

Then it tells us that if both doubled then the reaction is 8 times faster. Since from above Cl doubling causes it to increase 2x to get to 8x we need to multiply by 4. This means that doubling NO's concentration will increase the rate by 4 times. So again find the exponent that will make the number four times bigger. If originally [NO] = 1 and we double it to 2, then (2)^1 = 2. So 1 is not the exponent. (2)^2 = 4. So the exponent is 2 because that would increase the rate by 4.

The order of Cl is 1. The order of NO is 2. The overall order is the exponents of Cl and NO added together or 1+2 = 3.