Gen Chem Kaplan Q

[topdent1]

How did they add an extra row? I don't understand the explanation.

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Looking at lines 1 and 2, where the concentration of reactant A is held constant, we see that a doubling in the concentration of B results in a quadrupling of the rate, therefore the reaction is second order with respect to B. We can now look at lines 2 and 3 (or 1 and 3) to determine the required reaction order. From line 2 to line 3, the concentration of B is doubled; the reaction rate should thus quadruple due to the influence of the concentration increase of second order reactant B. We can divide out this quadrupling effect and create a hypothetical line 4:

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[mddang]

By comparing line #1, #2, and #3, you can figure out that the reaction rate is zero order with respect to the concentration of A.


If we were to hypothetically double the concentration of B and double the concentration of A, we would get line #4. Zero order with respect to [A], and second order with respect to . Doubling the concentration of A has no effect, while doubling the concentration of B causes a 4 fold increase in the initial rate of the reaction.