PS : ratio and proportions

[tanyatomar]

the rate of a certain reaction is directly proportional to concentration of chemical A and inversly proportional to concentration of chemical B. if concentration of chemical B is increased by 100%, which of the following is closest to the percent change required in concentration of A to keep the rate of reaction unchanged.

1.100% decrease

2. 50% decrease

3. 40% decrease

4. 40% increase

5. 50% increase

OA: 4. : 40% increase

why not 5. : 50% increase?? please explain..

[LazyNK]

Are you sure you have described the problem correctly ?
Why I ask is because as per your description:

If CA is concentration of A and CB is concentration of B.
Then Rate=k*(CA/CB) where k is a constant.
If CB increases by 100%, it becomes 2*CB. Let new concentration of A be CA'.
Since rate of reaction should remain unchanged,
Rate=k*(CA/CB)=k*(CA'/(2*CB))
->CA'=2*CA -> 100% increase, which is not even present in the answer choices.

Can you confirm ?
-NK

[shubham_sagijain]

the rate of a certain reaction is directly proportional to concentration of chemical A and inversly proportional to concentration of chemical B. if concentration of chemical B is increased by 100%, which of the following is closest to the percent change required in concentration of A to keep the rate of reaction unchanged.

1.100% decrease

2. 50% decrease

3. 40% decrease

4. 40% increase

5. 50% increase

OA: 4. : 40% increase

why not 5. : 50% increase?? please explain..

This is the correct problem statement :

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

Ans : D

[shubham_sagijain]

the rate of a certain reaction is directly proportional to concentration of chemical A and inversly proportional to concentration of chemical B. if concentration of chemical B is increased by 100%, which of the following is closest to the percent change required in concentration of A to keep the rate of reaction unchanged.

1.100% decrease

2. 50% decrease

3. 40% decrease

4. 40% increase

5. 50% increase

OA: 4. : 40% increase

why not 5. : 50% increase?? please explain..

This is the correct problem statement :

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

Ans : D

[RonPurewal]

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