# How much

?
• Created by: Holly45
• Created on: 09-03-15 17:58

## Relative formula mass

• usually the same number as the mass number
• the relative atomic masses added together
• eg: mgcl2 = 24 + (35.5 x 2) = 95
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## Empirical formula

1. Change the % given to the masses of each element in 100g compound

2. Change masses to moles (divide by Ar values)

3. This tells you the ratio

4. The simplest whole number ratio gives you the formula

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## Percentage yield

• yeild is the amount of product a chemical reaction makes
• percentage yeild is what we really get compared to what we might get

Percentage yeild = amount of product produced divided by maximum amount of produced product X 100

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## Why is a yeild not 100%

• reactions may be reversible
• some products might be lost in handling or left behind in equipment
• some chemical reactions may produce more than one product
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## Reversible reactions

• a reversible reaction is when the products of a reaction can be reacted to produce the original reactants
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