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rate and percentage

by parulmahajan89 » Thu Aug 16, 2012 8:44 pm
The rate of certain chemical reaction is directly proportional to square of Chemical A present and inversrly proportion to Chemical B present. If the concentration of Chemical B is increased by 100% then which of the following is the closest percentage in the concentration of Chemical A to keep the reaction rate unchanged?

a.100% decrease
b.50% decrease
C 40% decrease
d 40% increase
e 50% increase
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by natali » Thu Aug 16, 2012 8:53 pm
parulmahajan89 wrote:The rate of certain chemical reaction is directly proportional to square of Chemical A present and inversrly proportion to Chemical B present. If the concentration of Chemical B is increased by 100% then which of the following is the closest percentage in the concentration of Chemical A to keep the reaction rate unchanged?

a.100% decrease
b.50% decrease
C 40% decrease
d 40% increase
e 50% increase
suppose the rat of a certain chemical reaction is x
x/A^2
inversely is b/x
when B is increased by 100% mean B is increase 2B
to keep reaction unchanged, or A^2=2B or A= 1.4B
so it should increase 40%
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by Anurag@Gurome » Thu Aug 16, 2012 9:04 pm
parulmahajan89 wrote:The rate of certain chemical reaction is directly proportional to square of Chemical A present and inversrly proportion to Chemical B present. If the concentration of Chemical B is increased by 100% then which of the following is the closest percentage in the concentration of Chemical A to keep the reaction rate unchanged?

a.100% decrease
b.50% decrease
C 40% decrease
d 40% increase
e 50% increase
Rate of a certain chemical reaction, R, is directly proportional A²/B
When the concentration of chemical B is increased by 100 percent, then concentration of chemical A also increases by, say, a%.
Then, R = A²/B = (aA)²/2B
A²/B = a²A²/2B
1 = a²/2
a² = 2
a = 1.4, which means there is [spoiler]40% increase[/spoiler] in the concentration of chemical A.

The correct answer is D.
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