## Title

Method of Reacting Masses with Gases
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RuthSwallowxx
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Joined: 29/09/2012 - 14:27
Posts: 1
Method of Reacting Masses with Gases

Does anyone have the step by step method on how to do the reacting masses with gases callculation

chemistrysubjec...
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Joined: 10/06/2007 - 22:31
Posts: 347
I will use the "mole" method.

I will use the "mole" method. Some schools do and some don't. If this is no good, let me know and I will translate.

The mass of anything can be converted into a number of moles....

Mass = no of moles x relative formula mass

The volume of any gas at room temperature and pressure is 24 dm3.

The chemical equation tells you the link between how many moles of solid and how many moles of gas.

So, as an example...

What mass of hydrogen gas is produced when 2.4g of magnesium reacts with hydrochloric acid?

Mg + 2HCl -> MgCl2 + H2

2.4g of magnesium is 2.4/24 moles = 0.1 mol

equation says one mole of Mg gives one mole of H2, so 0.1 mol of Mg gives 0.1 mol of H2.

1 mol of H2 has a volume of 24 dm3, so 0.1 mol has a volume of 2.4 dm3.

If you are at A-level, you need to use the ideal gas equation. I can also help with that if necessary.