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# The rate of a certain chemical reaction is directly

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Manager
Joined: 22 Jun 2008
Posts: 104
Schools: Darden School of Business (Class of 2012)
The rate of a certain chemical reaction is directly [#permalink]

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19 Aug 2008, 09:22
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 concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

a)100% decrease
b)50% decrease
c)40% decrease
d)40% increase
e)50% increase

Pls. if you could provide detail explanation I am lost in this one.
Many tks! Lw

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Joined: 07 Nov 2007
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19 Aug 2008, 09:30
lordw wrote:
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 concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

a)100% decrease
b)50% decrease
c)40% decrease
d)40% increase
e)50% increase

Pls. if you could provide detail explanation I am lost in this one.
Many tks! Lw

Ca -- Concentration of A
Cb -- Concentration of B
r= k Ca^2/ Cb

to keep the rate constant r sould be same.
Ca^2/Cb = X^2/ 2Cb
X^2 = 2 Ca^2
x= sqrt(2) Ca = 1.414 Ca
~41% increase from the original.

D

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To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: Chemical reaction   [#permalink] 19 Aug 2008, 09:30
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# The rate of a certain chemical reaction is directly

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