Rate Law for A+B Reaction: k[A][B]^2

In summary, the rate law for a reaction involving two reactants, A and B, is represented as: Rate = k[A][B]^2. The rate constant (k) can be determined experimentally by measuring the initial rates of the reaction at different concentrations of reactants A and B. The exponents of the concentration terms in the rate law indicate the order of the reaction with respect to each reactant, and in this case, the reaction is second-order with respect to both A and B. If the concentration of one reactant is doubled, the rate of the reaction will increase by a factor of four. However, the rate law for a two-reactant reaction only applies to the forward reaction and cannot be used to predict the
  • #1
tica86
79
0
) If the rate law for the reaction
2A + 3B → products
is first order in A and second order in B, then the rate law is rate

I initially thought the answer would be k[A]^2 but it's wrong, the correct answer is
k[A]^2
Could anyone explain?? Please, thank you!
 
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  • #2
"first order in A" means "Proportional to [A]"

"Second order in B" means "Proportional to 2."

Put those together and what do you get?
 

What is the rate law for a reaction involving two reactants?

The rate law for a reaction involving two reactants, A and B, is represented as: Rate = k[A][B]^2, where k is the rate constant and [A] and [B] are the concentrations of reactants A and B respectively.

How is the rate constant (k) determined in a reaction with two reactants?

The rate constant (k) can be determined experimentally by measuring the initial rates of the reaction at different concentrations of reactants A and B, and then using these values to calculate the corresponding values of k. Alternatively, k can be determined using the integrated rate law for a second-order reaction: 1/[A]t = kt + 1/[A]0, where [A]t is the concentration of reactant A at a particular time, t, and [A]0 is the initial concentration of A.

What is the significance of the exponent of the concentration terms in the rate law for a two-reactant reaction?

The exponents of the concentration terms in the rate law for a two-reactant reaction indicate the order of the reaction with respect to each reactant. In this case, the reaction is second-order with respect to both A and B, meaning that the rate of the reaction is directly proportional to the square of the concentrations of both reactants.

How does the rate of the reaction change if the concentration of one reactant is doubled?

If the concentration of one reactant is doubled, the rate of the reaction will increase by a factor of four, since the rate law for a second-order reaction involves the square of the concentration terms. This shows that the rate of a reaction is highly dependent on the concentration of reactants.

Can the rate law for a two-reactant reaction be used to predict the rate of the reverse reaction?

No, the rate law for a two-reactant reaction only applies to the forward reaction. The rate law for the reverse reaction may have a different form and would need to be determined experimentally.

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