Describe what happens to the mass of a reaction mixture when a gas is absorbed during a chemical reaction in an open system.

When a gas is absorbed during a chemical reaction in an open system, the mass of the reaction mixture increases. This is because the gas molecules are taken into the mixture, contributing to the total mass measured.

This question evaluates the student's ability to explain the effect of gas uptake on mass in a chemical reaction. It reinforces the concept of mass conservation by linking the absorption of gas to an increase in mass, which is crucial for understanding chemical reactions involving gases.