For a zeroth-order reaction, what are the units of the rate constant k?

• A. mol^{-1} L s^{-1}
• B. s^{-1}
• C. L mol^{-1} s^{-1}
• D. mol L^{-1} s^{-1}

Answer: (D)

Verified step by step guidance

1. Recall the general rate law for a reaction: \(\text{rate} = k [A]^n\), where \(k\) is the rate constant, \([A]\) is the concentration of the reactant, and \(n\) is the order of the reaction.
2. For a zeroth-order reaction, the rate law simplifies to \(\text{rate} = k\), because the reaction rate is independent of the concentration of the reactant (\(n=0\)).
3. The rate of reaction is typically expressed in units of concentration per time, such as \(\mathrm{mol \\cdot L^{-1} \\cdot s^{-1}}\).
4. Since the rate equals \(k\) directly for a zeroth-order reaction, the units of \(k\) must be the same as the units of the rate, which are \(\mathrm{mol \\cdot L^{-1} \\cdot s^{-1}}\).
5. Therefore, the units of the rate constant \(k\) for a zeroth-order reaction are \(\mathrm{mol \\cdot L^{-1} \\cdot s^{-1}}\).