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Mass calculations

How do I solve this problem?
Calculate the relative molecular mass of a gas which has a density of 2.615 g dm^-3 at 298K and 101kPa?

Reply 1

Sodium229

I think you need to use the ideal gas equation for this question, pV=nRT, where R is the gas constant, 8.314 J mol^-1 K^-1. You are told that for every volume of 1 dm^3 there is 2.615g of the gas, so the V in pV=nRT is 0.001 m^3, as the volume of gas is measured in m^3, not dm^3. You can rearrange this equation to find the number of moles, n. So n=pV/RT.
You can then use the equation: relative molecular mass = mass / moles to find the Mr of the gas.
Hope this helps! :smile: