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# For a reaction that is first order with respect to [D] and second order with respect to [E], which o

For a reaction that is first order with respect to [D] and second order with respect to [E], which of the following will result in no change in overall reaction order?

A. Doubling [D] and halving [E]

B. Halving [D] and doubling [E]

C. Doubling [D] and doubling [E]

D. Increasing [D] by a factor of four and halving [E]

Solution: We can write the rate law based on the given.

The orders are powers in the rate law equation.

Rate = k [D][E]^2

Let's go through each answer choice to figure out the correct one.

A. Doubling [D] and halving [E]

Rate = k [2D][1/2E]^2 = 2*(1/4) = 1/2 NOT 1

The rate law would be 1/2 of the original, answer choice A is not correct

B. Halving [D] and doubling [E]

Rate = k [1/2D][2E]^2 = 1/2(4) = 2 , not correct

C. Doubling [D] and doubling [E]

Rate = k [2D][2E]^2 = 2(4) = 8 , not correct

D. Increasing [D] by a factor of four and halving [E]

Rate = k [4D][1/2E]^2 = 4(1/4) = 1

The rate stays the same! Answer choice D is the correct answer.