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Moles

Volumes of Gases.

A reaction was found to produce two litres of Chlorine.
 What is the mass of 2 litres of chlorine?

Method.
 1) Find how many moles of chlorine are present in 2 litres.

One mole of any gas occupies a volume of 24,000 cm3 (24 litres).
1 litre = 1,000 cm3,  2 litres = 2,000 cm3.

The equation which converts volume into moles is

moles = volume (in cm3) ÷ 24,000

moles =  2,000 ÷ 24,000
                          =  0·083 moles of chlorine.

2) What is the mass of 0·083 moles of chlorine?

One mole of chlorine gas contains one mole of chlorine molecules.
Each chlorine molecule contains two chlorine atoms,
so use the relative molecular mass.  RMM of Cl2  = 71.

mass = moles x RFM

mass =  0·083 x 71
                      =  5·89 g of chlorine.

So, 2 litres of chlorine has a mass of 5·89 g.

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