In the ideal gas calculation, what is the unit of the volume input?

• A. Liters
• B. Cubic meters
• C. Gallons
• D. Milliliters

Answer: (A)

Volume in ideal-gas calculations is chosen to match the gas constant you’re using. In most problems, the common form of R is 0.0821 L·atm/(mol·K), which pairs naturally with pressure in atmospheres, temperature in kelvin, and volume in liters. Keeping volume in liters makes PV = nRT straightforward and yields n directly in moles. Using cubic meters would require a different form of R (8.314 Pa·m^3/(mol·K)) and pressure in pascals, which adds extra steps. Milliliters would work only if you convert to liters to keep the units consistent, and gallons would require more conversions. So liters is the standard volume unit in these ideal-gas calculations.