C2 3.3 Percentages and formulae

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C2 3.3 Percentages and formulae
What is the percentage mass of Hydrogen in
methane CH4 C12, H1 ?
Adding RAMs
12 (1x4) 16
Mass of Element as a fraction of compound
4 16
X by 100
4 x 100 16
25
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C2 3.3 Percentages and formulae
What is the percentage mass of Nitrogen in the
fertiliser, Ammonium nitrate NH4NO3 H 1,
N 14, O 16 ?
Adding RAMs
14 ( 1 x4) 14 ( 16 x 3 ) 80
Mass of Element as a fraction of compound
28 80
X by 100
28 x 100 80
35
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C2 3.3 Percentages and formulae
What is the formula of aluminium chloride if 9g
of aluminium reacts with 35.5g of chlorine ?
(RAMs Al 27g, Chlorine 35.5g)
Divide mass by RAM (1st. Element)
For aluminium 9 0.333
27
For chlorine 35.5 1.00
35.5
Divide mass by RAM (2nd. Element)
Divide by smallest to find ratio
0.333 1 0.333
1.000 3 0.333
The formula of aluminium chloride is AlCl3
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C2 3.3 Percentages and formulae
What is the formula of a compound which contains
16g of sulfur and 24g of oxygen? (RAMs S
32g, Oxygen 16g)
Divide mass by RAM (1st. Element)
For sulfur 16 0.5
32
For oxygen 24 1.50
16
Divide mass by RAM (2nd. Element)
Divide by smallest to find ratio
0.5 1 0.5
1.5 3 0.5
The formula of sulfur trioxide is SO3
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