1. The problem statement, all variables and given/known data Two glass vessels M and N are connected by a closed valve. M contains helium at 20 °C at a pressure of 1 × 10^5 Pa. N has been evacuated, and has three times the volume of M. In an experiment, the valve is opened and the temperature of the whole apparatus is raised to 100 °C. What is the final pressure in the system? A 3.18 × 10^4 Pa B 4.24 × 10^4 Pa C 1.25 × 10^5 Pa D 5.09 × 10^5 Pa 2. Relevant equations PV=nRT Where R=8.31J/Kmol 3. The attempt at a solution For M T=20 °C = 298 K P= 10^5 Pa V= x For N V =3x T =100°C = 373K Now do I find the change in the T and V and use PV=nRT to calculate the change in the P and then find the final P? But I do not know the mass of helium, so I can not find the number of moles.