If we have 10 grams of Helium at a concentration of 10 mol dm-3, what volume of helium do we get.

First we need to identify that 2 equations will be in use here. 1st - moles = mass/Mr and 2nd - volume = moles/concentration This is because we need to find the volume and the only other information we have is the mass, the Mr (from the periodic table) and the concentration. So if we can start by finding the moles from the first equation, we can then use the second equation to find the volume. moles = 10/2 so moles = 5 Volume = 5/10 so volume = 0.5 dm3