A student plans to calculate the molar mass of an unknown gas from the mass of a measured volume of gas at a known temperature and pressure. To how many significant figures should the student report the molar mass if 175.0 mL of the gas weighs 1.0315g at a temperature of 22°C and pressure of 742 mmHg?
I thought that it would be two significant figures since the temperature's 22°C and everything is either multiplication or division, but the answer is three. Does the temperature count as an exact number, and if so, why? Or is there something else I'm missing?