ideal gases. what fun. please help!! i'm having problems getting sensible answers... 1. a cylinder contains 4.62g of hydrogen at 17C and 2.32 x10^6 Pa calculate number of moles. actual mass/molecular mass= 4.62/2= 2.31 (relative molecular mass given as 2 in the question...is this right??) calculate density of gas. density=mass/volume volume: using pV=nRT V=nRT/p =2.31x8.31x(17+273) all divided by 2.32x10^6 =0.00239951... density=4.62x10^3 (to make it into kg) divided by 0.00239951... gives 1925393.101... kgm^-3 which seems awfully high. i have another question but i'll put it in another thread before my computer crashes and i lose all of this.