If I have 21 moles of gas held at a pressure of 78 atm and a temperature of 900 K, what is the volume of the gas?

Answer 1

You would use the Ideal Gas Law to find your answer which says PV = nRT where "P" is pressure, "V" is volume, "n" is the number of moles, "R" is the Ideal Gas Constant which, in appropriate units for this problem is 0.082057 L atm/(mole K), and T is absolute temperature.

You are given n = 21 moles, P = 78 atm, T = 900 K so just plug those in and solve for "V"