Posted by **Annabel** on Wednesday, January 31, 2007 at 8:29am.

I need to work out the density of the gaseous oxide of arsenic at STP in g L-1

I realise density = mass/volume but my answer works out very high!! I have already worked out the volume to be 52cm^3 (Cubed). the mass to start with was 0.702g and at the end of the reaction was 0.927g. I know this isn't difficult and my figures are wrong!!!

I have tried 0.927g/0.052g but get 18 L-1. So whether I use the difference in the mass I don't know, i.e. 0.225/0.052g gives 4.32g L-1

Does any of this make sense to anyone? This is annoying me so much and is worth only 2 marks...

From your statement, I have no idea what you are doing.

You need the mass of the oxide only, not the collection vessel. You need the volume of the gas.

density=mass/volume. If the mass is in grams, and the volume in cm cubed, then the density will be in g/cubic cm.

thanks Bob, sorry to confuse you, I confuse myself!!! I understand I only need the oxide.