The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased 100%, 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% decrese
c) 40% decrease
d) 40% increase
e) 50% increase
Answer is D.
Can someone help me out with an equation and a picking numbers scenario?
GMAT Prep - Mixtures - percentages
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Let
A1=original concentration of A
B1= Original concentration of B
Chemical Reaction (CR1)=k*A1^2/B1
Let the new Chemical Reaction be CR2
Let the new Concentration of Chemical B be B2
A2=New concentration of Chemical A
Acc to the question
B2=2B1 (100% increase)
Therefore to keep the reaction rate unchanged CR1=CR2
K*A1^2/B1=K*A2^2/B2
Since B2=2B1
K*A1^2/B1=K*A2^2/2B1
or A1^2=A2*^2/2
or 2A1^2=A2^2
or 1.414A1=A2
Therefore 40% increase
Answer D
A1=original concentration of A
B1= Original concentration of B
Chemical Reaction (CR1)=k*A1^2/B1
Let the new Chemical Reaction be CR2
Let the new Concentration of Chemical B be B2
A2=New concentration of Chemical A
Acc to the question
B2=2B1 (100% increase)
Therefore to keep the reaction rate unchanged CR1=CR2
K*A1^2/B1=K*A2^2/B2
Since B2=2B1
K*A1^2/B1=K*A2^2/2B1
or A1^2=A2*^2/2
or 2A1^2=A2^2
or 1.414A1=A2
Therefore 40% increase
Answer D
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Nice way to calculate it.....ankanas wrote:Let
A1=original concentration of A
B1= Original concentration of B
Chemical Reaction (CR1)=k*A1^2/B1
Let the new Chemical Reaction be CR2
Let the new Concentration of Chemical B be B2
A2=New concentration of Chemical A
Acc to the question
B2=2B1 (100% increase)
Therefore to keep the reaction rate unchanged CR1=CR2
K*A1^2/B1=K*A2^2/B2
Since B2=2B1
K*A1^2/B1=K*A2^2/2B1
or A1^2=A2*^2/2
or 2A1^2=A2^2
or 1.414A1=A2
Therefore 40% increase
Answer D
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my gut reaction to this is to keep the whole thing in an easier perspective and pick numbers is there a way to do that!?
Appetite for 700 and I scraped my plate!