Question

please help with the question 4 b iii)

Answer 1

@Vincent-Lyon.Fr

Answer 2

I'm not sure what the cause of your trouble is, but maybe this will help clarify things.

I think the question is getting you to think about what will happen when the valve is opened.

Since the surroundings constitute a very large system, you would expect that a cylinder full of some gas will not be able to really change the surroundings very much.

In this way, you would do the problem under the assumption that the surroundings will remain the same.

Equilibrium means that the cylinder has to be the same as the surroundings.

Therefore, the cylinder contents will change to match the surroundings.

So I believe the calculation just requires the ideal gas law. Simply adjust the values for the new values the cylinder will have to achieve. This leaves you with only one variable changing, 'n'. Then through multiplying 'n' by the molar mass you should arrive at a mass.