What is the molecular weight of an unknown gas if 2.5g of it occupies 2L at 630 torr and a temperature of 600K

Question

And: If a 360mL sample of helium contains 0.25 mol of the gas, how many molecules of chlorine gas would occupy the same volume at the same temp. and pressure?

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if you could explain how to solve the problems (rather than just answer), it would be greatly appreciated

Answer 1

assuming ideal gas.

given P, T, and V. use ideal gas law PV=nRT to solve for n.

R is the ideal gas constant

given n (number of moles) and m (2.5g)

MW=m/n (g/mol)

for number 2. assuming ideal gas. 0.25 mol He at same T and P occupies same volume of gas as 0.25 mol Cl. This is because an ideal gas is a point mass with no volume. from moles you should be able to get molecules (google it).

If it is not an ideal gas the problems are more complicated and fugacity will have to be considered.