A first-order reaction has an initial reactant concentration of 0.5 mol L ⁻¹ . After exactly 30 s , the concentration is found to be 5 10⁻⁴ mol L ⁻¹ . The rate constant for this reaction is:

Step-by-step solution

For a first-order reaction, the rate constant k is given by: k = 2.303 t [A]₀ [A]_t Given: [A]₀ = 0.5 mol L ⁻¹ [A]_t = 5 10⁻⁴ mol L ⁻¹ t = 30 s Substituting the values: k = 2.303 30 ( 0.5 5 10⁻⁴ ) k = 2.303 30 (10^3) k = 2.303 30 3 k = 2.303 10 = 0.2303 s ⁻¹ Answer: 0.2303 s ⁻¹