Equations Simplified Revision Notes for GCSE AQA Chemistry Combined Science

Revision notes with simplified explanations to understand Equations quickly and effectively.

Learn about Simple Model of the Atom for your GCSE Chemistry Combined Science Exam. This Revision Note includes a summary of Simple Model of the Atom for easy recall in your Chemistry Combined Science exam

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1.1.3 Equations

Using Chemical Formulae

Compounds are represented using a formula made up of the symbols of the elements they contain.

Compound	Formula	No. of Elements	No. of Atoms
Sodium Chloride	NaCl	2	2 (1 Na, 1 Cl)
Sodium Hydroxide	NaOH	3	3 (1 Na, 1 O, 1 H)
Sodium Oxide	Na₂O	2	3 (2 Na, 1 O)
Sodium Sulfate	Na₂SO₄	3	7 (2 Na, 1 S, 4 O)
Calcium Carbonate	CaCO₃	3	5 (1 Ca, 1 C, 3 O)

infoNote

Worked Example Question: Question: What is the total number of atoms in the formula $(NH_4)_2SO_4$ , ammonium sulfate?

Solution:

$(NH_4)_2$ becomes…

2×NH_4 = (2×N)+(2×H4)=(2×N)+(8×H)

$SO_4$ becomes…

1×SO_4 = (1×S)+(1×O_4)=(1×S)+(4×O)

So…

\text{Total atoms} = (2 \times N) + (8 \times H) + (1 \times S) + (4 \times O) = 15 \text{ atoms}

Final Answer: Total = 15 Atoms

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