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# The rate of a certain chemical reaction is directly

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Intern
Joined: 12 Jun 2006
Posts: 1
The rate of a certain chemical reaction is directly [#permalink]

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26 Feb 2007, 13:32
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentrationof chemical B present. If the concentration of chemical B is increased by 100 %, which of the following is closet to the percent change in the concentration of chemical A required to keel the reaction rate unchanged?

A)100 % decrease
B) 50 % decrease
C) 40 % decrease
D) 40 % increase
E) 50 % increase

ANYBODY CAN EXPLAIN THIS PROBLEM FOR ME???
Intern
Joined: 22 Feb 2007
Posts: 3

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26 Feb 2007, 14:06
50% ?

What's the OA ?
Manager
Joined: 01 Apr 2006
Posts: 180

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26 Feb 2007, 15:13
My answer is D (40% increase)

R (rate) is directly proportional to A^2 / B.

If B is doubled (i.e. increased by 100%), then the new A must be sqr(2) * A_original. Since sqr(2) is about 1.4, therefore the new A must be increased by 40% to keep the overall rate unchanged.
Senior Manager
Joined: 24 Oct 2006
Posts: 339

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27 Feb 2007, 09:28
Was discussed before. You could search.
Manager
Joined: 01 Apr 2006
Posts: 180

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27 Feb 2007, 13:42
Thanks Sumithra... I found one good response:

http://www.gmatclub.com/phpbb/viewtopic.php?t=40676
27 Feb 2007, 13:42
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