How To Determine The Units Of The Rate Constant K  Chemical Kinetics  Summary and Q&A
TL;DR
This lesson explains how to calculate the units of the rate constant (k) for different order reactions.
Questions & Answers
Q: How do you calculate the units of k for a zeroorder reaction?
In a zeroorder reaction, where rate = k, the units of k are molarity per second (mol/L/s).
Q: What are the units of k for a firstorder reaction with respect to a and overall?
In a firstorder reaction with respect to a and overall, the units of k depend on the given time unit. For example, if the rate is given as mol/L/min, then the units of k are minutes to the negative 1 power (1/min).
Q: How do you determine the units of k for a secondorder overall reaction?
In a secondorder overall reaction, the units of k can be calculated using the formula. For example, if the rate is given as molarity per hour (mol/L/h), then the units of k are liters per mole per hour (L/mol/h).
Q: Is there an alternative method to calculate the units of k without using the formula?
Yes, you can isolate k in the rate law expression, divide both sides by the concentrations, and replace them with their units to determine the units of k. This method can provide the same result as using the formula.
Summary & Key Takeaways

For a zeroorder reaction, the units of k can be calculated as molarity per second (mol/L/s).

In a firstorder reaction, the units of k depend on the time unit given (e.g., minutes or hours).

For a secondorder overall reaction, the units of k are liters per mole per hour (L/mol/h).