### Higher Chemistry - Gas Volumes

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Messages: 1 - 2 of 2
• #### Message 1.

Posted by MissChemTeacher_Bitesize (U15172316) on Sunday, 2nd December 2012

Hey Guys!

Here is a problem from the 2012 past paper.

Which of the following pairs of gases occupy the same volume?

(Assume all measurements are made under the same conditions of temperature and pressure.)

A 2 g hydrogen and 14 g nitrogen
B 32 g methane and 88 g carbon dioxide
C 7 g carbon monoxide and 16 g oxygen
D 10 g hydrogen chloride and 10 g sulphur dioxide

I'll put a solution on the board in a few days.

Miss_Chem

• #### Message 2

, in reply to message 1.

Posted by MissChemTeacher_Bitesize (U15172316) on Thursday, 6th December 2012

Hey Guys!

To work this out, you should know that one mole of any gas occupies the same volume.

We can use number of moles = mass / gfm

This will tell us how many moles of each gas we have, so any combinations where the number of moles are the same will occupy the same volume.

Remember that oxygen, hydrogen and nitrogen are diatomic.

A 2g of H₂ = 1 mole and 14g of N₂ = 0.5 moles
B 32g of CH₄ = 2 moles and 88g of CO₂ = 2 moles
C 7g of CO = 0.25 moles and 16g of O₂ = 0.5 moles
D 10g of HCl = 0.27 moles and 10g of SO₂ = 0.15 moles

The answer here must be B. As each combination has the same number of moles of gas, they will occupy the same volume.

Cheers Miss_Chem

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