Chemistry questions below

Question

The label fell off a tank of compressed gas. Although the colour of the tank provides information about the identity of the gas, the company selling the gas wanted to confirm what gas is in the tank. They filled a 98.0 mL container with 0.0810 g of the gas. The pressure of the gas was 101.3 kPa, and the temperature was 25 °C.

Assuming the gas acts as an ideal gas, what is the molar mass of the gas? From the molar mass of the gas, identify the gas. Assume that the gas is an element, not a compound or a mixture. Which gas law did you use to solve this problem?

Answer 1

Must use the full ideal gas law (answer to last question) to solve this, PV = nRT and solve for moles n. Since the pressure of 101.3 kPa is 1 atmosphere, I'll use this. n = PV/RT = (1 atm) (0.098 L) / [(0.08206 atm L/mol K) (273 + 25 K) = 0.00400 mole. Having 0.0810g of this gas, the molar mass is 20.2 g/mol, which matches neon Ne.