Answer:
6.30 M⁻¹s⁻¹.
Explanation:
As the reaction is first order with respect to a and b.
The rate of the reaction = k [a][b],
where, k is the rate constant of the reaction.
The rate of the reaction = 2.65 × 10⁻⁴ M/s,
[a] = 1.60 × 10⁻² M,
[b] = 2.67 × 10⁻³ M.
∴ k = (the rate of the reaction / [a][b]) = (2.65 × 10⁻⁴ M/s) / (1.60 × 10⁻² M)( 2.67 × 10⁻³ M) = 6.30 M⁻¹s⁻¹.