First-order reaction concentration after 20 minutes

Practice question

Question

A first-order reaction has an initial concentration of 0.5 mol L⁻¹ and a rate constant of 0.0693 min⁻¹. What is the concentration after 20 minutes?

Choose one · Correct answer highlighted

0.25 mol L⁻¹ 0.1 mol L⁻¹ 0.125 mol L⁻¹ Correct 0.05 mol L⁻¹

[R] = 0.5 / 4 = 0.125 mol L⁻¹.

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