What is the unit of pressure commonly used in gas law equations?

The commonly used unit of pressure in gas law equations is the atmosphere (atm). This unit is particularly relevant because many gas laws, such as the ideal gas law, were historically formulated based on standard atmospheric conditions. One atmosphere is defined as being equal to 101.325 kilopascals, which makes it a convenient reference point for many calculations involving gases under standard conditions.

While other units like Pascals, millimeters of mercury, and bars are also valid units of pressure, the atmosphere remains a widely accepted standard in chemistry, especially when discussing behavior of gases at different pressures. In many educational contexts and practical applications, the use of atmospheres simplifies the calculations and relationships between various gas quantities, such as volume, temperature, and amount of substance. This makes it easier for students to apply gas laws without constantly converting between different units of pressure.