GCSE SCIENCE CHEMISTRY HIGH SCHOOL - Moles - Calculating the Empirical Formula from a Reaction - Calcium Chloride - Mole

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The Empirical Formula from a Reaction.

Example 2.

20 g of calcium was found to react with 35·5 g of chlorine.
What is the empirical formula of calcium chloride?

Method.
1) Find how many moles of calcium react with how many moles of chlorine.
RAM of Ca = 40, RAM of Cl = 35·5.

moles = mass ÷ RAM

for calcium moles = 20 ÷ 40
= 0·5 moles.

for chlorine moles = 35·5 ÷ 35·5
= 1·0 moles.

2) The proportion of moles of calcium to moles of chlorine
is reduced to the lowest whole number.

0·5 moles of Ca to 1·0 moles of Cl.
Multiply by 2.
1 mole of Ca to 2 moles of Cl.
The empirical formula is CaCl₂.

Since calcium chloride is an ionic compound,
the actual formula is the same as the empirical formula.