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For a reaction involving A and B, the rate expression is Rate = k[A]^n[B]^m If the concentration of A is made twice and the concentration of B is reduced to one-half, then the new rate compared with the original rate is given by:

1. m + n
2. n - m
3. 2^(n - m)
4. 1/2^(m + n)

Correct answer: n - m

Solution

The new rate can be calculated by substituting the modified concentrations into the rate expression. When A is doubled, its contribution increases by a factor of 2^n, and when B is halved, its contribution decreases by a factor of (1/2)^m. Therefore, the overall change in rate is 2^n / 2^m, which simplifies to 2^(n - m), confirming that the correct option is n - m.

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