Question

State the order of reaction whose rate constant possess the following unit:

hour⁻¹

Answer 1

If the unit of the rate constant k is hour⁻¹, that means it has only the reciprocal of time in its units, without any concentration term.

From the general formula for units of k for an n-th order reaction:

Units of k = (concentration)¹⁻ⁿ ⋅ time⁻¹

For the units to be just time⁻¹, the concentration term must be (concentration)⁰, which happens when:

1 − n = 0

n = 1

∴ The reaction is of first order.