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Chemical reaction

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Chemical reaction [#permalink]

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New post 28 Mar 2009, 07:23
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A
B
C
D
E

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The rate of a chemical reaction is directly proportional to concentration of A^2 and inversely proportional to concentration of B. If concentration of B is increased by 100%, which of the following is closest to the percent change in concentration of A, so that the reaction rate remains unchanged.

a) 100% decrease
b) 50% decrease
c) 40% decrease
d) 40% increase
e) 50% increase
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Re: Chemical reaction [#permalink]

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New post 28 Mar 2009, 07:58
It has to be either A, B or C.
I would go for B.

What is the OA?

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Re: Chemical reaction [#permalink]

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New post 28 Mar 2009, 09:41
The rate of a chemical reaction is directly proportional to concentration of A^2 and inversely proportional to concentration of B. If concentration of B is increased by 100%, which of the following is closest to the percent change in concentration of A, so that the reaction rate remains unchanged.

R(reaction)-->A^2
R--->(1/B)
where
"--> means Proportional too"

Now R -->A^2/B
==>A^2-->B(R is constant)

Now B becomes 2B(100% increase means doubling)
hence New A becomes 41.4 A

hence its D

because root 2=1.414
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Last edited by nitya34 on 28 Mar 2009, 10:24, edited 1 time in total.

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Re: Chemical reaction [#permalink]

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New post 28 Mar 2009, 10:02
nitya34 wrote:
The rate of a chemical reaction is directly proportional to concentration of A^2 and inversely proportional to concentration of B. If concentration of B is increased by 100%, which of the following is closest to the percent change in concentration of A, so that the reaction rate remains unchanged.

R(reaction)-->A^2
R--->(1/B)
where
"--> means Proportional too"

Now R -->A^2/B
==>A^2-->B(R is constant)

Now B becomes 2B(100% increase means doubling)
hence New A becomes 41.4 A

hence its D

because root 2=1.414

hence New B becomes


You mean A becomes 1.4A, right?

This is an interesting problem. I also agree the answer should be D, but 1.4^2 is less than 2, so technically, D should not apply as well. :-D

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Re: Chemical reaction [#permalink]

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New post 28 Mar 2009, 10:21
Thanks for the explanation. That actually makes it more clear.
It's just an approximation - so the answer is correct - 40% increase.

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Re: Chemical reaction [#permalink]

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New post 28 Mar 2009, 10:26
Yes
we have to find "closest to the percent change "
so 41.4% becomes 40% here :)
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Re: Chemical reaction [#permalink]

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New post 28 Mar 2009, 20:41
thanks a lot. Answer is D.
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Re: Chemical reaction   [#permalink] 28 Mar 2009, 20:41
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