Answer: If a reaction produces a gas such as oxygen or carbon dioxide, there are two ways to measure the reaction rate: using a gas syringe to measure the gas produced, or calculating the reduction in the mass of the reaction solution.
Explanation:
https://courses.lumenlearning.com/introchem/chapter/measuring-reaction-rates/#:~:text=If%20a%20reaction%20produces%20a,mass%20of%20the%20reaction%20solution.
This is the site I got it from. I hope this helps.