Question

Which one of the following sets of units is appropriate for a second-order rate constant?A. s-1B. mol L-1 s-1C. L mol-1 s-1D. mol2 L-2 s-1E. L2 mol-2 s-1

Answer 1

Answer:

E

Explanation:

A second order reaction is one in which the reaction rate is proportional to the concentrations of the 2 reactants. We only consider the reactants whose concentration are changing however.

For example, in the case:

A + B ----> C + D , provided that both A and B undergo concentration changes, the rate is proportional to the product of their concentrations.

Now, like we know, the unit of the reaction rate is per second I.e 1/s or simply s^-1 . Also it is important to note that the concentration of the reactants is exprested in units of mol/L. We can now mathematically calculate the unit of the rate constant.

Mathematically,

R = k × [A] [B]

Hence,

S^-1 = k × (mol/L)(mol/L)

S^

s^-1 = k × (mol/L)^2

K = s^-1 ÷ (mol/L)^2

K = s^-1 × L^2 × mol^-2.