True or False: A semi-log plot makes a zero-order kinetics equation appear as a straight line.

True or False: A semi-log plot makes a zero-order kinetics equation appear as a straight line.

• A. Not applicable
• B. True
• C. False
• D. Depends on concentration

Answer: (C)

A semi-log plot, where you plot the logarithm of concentration versus time, is used because first-order kinetics produce a straight line: ln[A] = ln[A]0 − k t. For zero-order kinetics, the concentration changes linearly with time according to [A] = [A]0 − k0 t. If you take the log of that expression, log([A]0 − k0 t), the result is not a straight line with time; it curves. Therefore, a semi-log plot does not make a zero-order equation appear as a straight line. To get a straight line for zero-order kinetics, plot concentration directly versus time.

A semi-log plot, where you plot the logarithm of concentration versus time, is used because first-order kinetics produce a straight line: ln[A] = ln[A]0 − k t. For zero-order kinetics, the concentration changes linearly with time according to [A] = [A]0 − k0 t. If you take the log of that expression, log([A]0 − k0 t), the result is not a straight line with time; it curves. Therefore, a semi-log plot does not make a zero-order equation appear as a straight line. To get a straight line for zero-order kinetics, plot concentration directly versus time.