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- Feb 7, 2008
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Guys I really need your help for a question on the Kaplan Subject Test General Chemistry. Please help if you can explain why.
If you guys have a hold of the subject test it is question number 2 of the first Kaplan Subject test for GCHEM. The answer explanation is confusing and basically I DON'T UNDERSTAND THE ANSWER!
Here it goes:
For the reaction A + B -> C, determine the order of the reaction with respect to B from the information given below.
Initial [A] (M) Initial (M) Initial Rate of formation of C
2.5 x 10^-6 3 x 10 ^ -4 5 x 10 ^ -3
5 x 10 ^-6 3x 10 ^ -4 1x 10 ^ -2
1 x 10 ^ -5 9 x 10 ^-4 1.8 x 10 ^ -1
a. zero order
b. first order
c. second order
d. third order
e. fourth order
So the answer apparently is C which I really don't understand why...
Since we are talking about the initial concentrations of B, we look at the change from (in this case from 3 x 10 ^-4 to 9 x 10 ^ -4). Dividing them gives you 3. Okay chill, then we look at the rate formation in order to find the order of reaction. So 1.8 x 10 ^ -1 / 1 x 10 ^ -2 is 18. I don't understand how you get a second order from 3^(3) = 27. The explanation in Kaplan is more than useless so I'm not going to even bother with it. If ANYONE on this form can explain the answer to me that would be greatly appreciated.
If you guys have a hold of the subject test it is question number 2 of the first Kaplan Subject test for GCHEM. The answer explanation is confusing and basically I DON'T UNDERSTAND THE ANSWER!
Here it goes:
For the reaction A + B -> C, determine the order of the reaction with respect to B from the information given below.
Initial [A] (M) Initial (M) Initial Rate of formation of C
2.5 x 10^-6 3 x 10 ^ -4 5 x 10 ^ -3
5 x 10 ^-6 3x 10 ^ -4 1x 10 ^ -2
1 x 10 ^ -5 9 x 10 ^-4 1.8 x 10 ^ -1
a. zero order
b. first order
c. second order
d. third order
e. fourth order
So the answer apparently is C which I really don't understand why...
Since we are talking about the initial concentrations of B, we look at the change from (in this case from 3 x 10 ^-4 to 9 x 10 ^ -4). Dividing them gives you 3. Okay chill, then we look at the rate formation in order to find the order of reaction. So 1.8 x 10 ^ -1 / 1 x 10 ^ -2 is 18. I don't understand how you get a second order from 3^(3) = 27. The explanation in Kaplan is more than useless so I'm not going to even bother with it. If ANYONE on this form can explain the answer to me that would be greatly appreciated.