Define the relative formula mass of a compound.

It is the sum of the relative atomic masses of all the atoms shown in the formula of the compound.

How does the total of the relative formula masses of the reactants compare with that of the products in a balanced equation?

They are equal, provided each formula is counted the number of times shown by its balancing number.

For 2H₂ + O₂ → 2H₂O, show that the totals of relative formula mass are the same on both sides, given H = 1 and O = 16.

The reactants total 2 × 2 + 32 = 36 and the products total 2 × 18 = 36, so both sides come to 36.

How is the percentage by mass of an element in a compound calculated?

Divide the total relative atomic mass of that element in the formula by the relative formula mass of the compound, then multiply by 100.

AQA GCSE Combined Science Chemistry 8464

Atomic Structure and the Periodic Table

Topic overview Atoms, elements and compounds Word equations, symbols and balanced equations Mixtures From the plum pudding model to the nuclear model Bohr, Chadwick and the modern model of the atom Relative electrical charges of subatomic particles Size and mass of atoms Relative atomic mass and electronic structure The periodic table Development of the periodic table Metals and non-metals Group 0 Group 1 Group 7

Bonding, Structure, and the Properties of Matter

Topic overview Chemical bonds, including metallic bonding Ionic bonding Ionic compounds Covalent bonding and how it is represented The three states of matter and changes of state Predicting state, state symbols, and the limits of the particle model Properties of ionic compounds Properties of small molecules Polymers and giant covalent structures Properties of metals and alloys, and why metals conduct Diamond and graphite Graphene and fullerenes

Chemical Analysis

Topic overview Pure substances Formulations Chromatography Tests for hydrogen, oxygen, carbon dioxide and chlorine

Chemical Changes

Topic overview The reactivity series Metal oxides, extraction, and redox in terms of electrons Acids reacting with metals, neutralisation and salts Soluble salts The pH scale and neutralisation Strong and weak acids The process of electrolysis, and molten ionic compounds Using electrolysis to extract metals Electrolysis of aqueous solutions Representation of reactions at electrodes as half equations

Chemistry of the Atmosphere

Topic overview The Earth's early atmosphere How oxygen increased and carbon dioxide decreased The gases in today's atmosphere, and which are greenhouse gases Human activities which contribute to an increase in greenhouse gases in the atmosphere Global climate change and carbon footprints Atmospheric pollutants from fuels, and their effects

Energy Changes

Topic overview Exothermic and endothermic reactions Everyday uses, and investigating temperature change Reaction profiles The energy change of reactions

Organic Chemistry

Topic overview Crude oil, hydrocarbons and alkanes Fractional distillation and petrochemicals Properties of hydrocarbons Cracking, and testing alkenes with bromine water Why cracking is useful, and equations for it

Quantitative Chemistry

Topic overview Conservation of mass and balanced chemical equations Relative formula mass and concentration of solutions Mass changes when a gas is involved, and measurement uncertainty Moles Amounts of substances in equations, and balancing using moles Limiting reactants

The Rate and Extent of Chemical Change

Topic overview Measuring the mean rate of a reaction Rate from graphs, and the gradient of a tangent Factors which affect the rates of chemical reactions Collision theory and activation energy Catalysts Reversible reactions and dynamic equilibrium The effect of changing conditions on equilibrium The effect of changing concentration The effect of temperature changes on equilibrium The effect of pressure changes on equilibrium

Using Resources

Topic overview Using the Earth's resources and sustainable development Producing potable water in the UK Desalination, and analysing water samples Waste water treatment Alternative methods of extracting metals Life cycle assessment Ways of reducing the use of resources

Quantitative Chemistry

Relative formula mass and concentration of solutions

3 things to know
Chemistry Paper 1

Overview

Defining and calculating relative formula mass, showing both sides of a balanced equation total the same, percentage by mass of an element, and concentration in g/dm³ from the mass of solute and the volume of solution.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

Calculate the percentage by mass of oxygen in CO₂, given relative atomic masses C = 12 and O = 16.

Numbers

Calculate the percentage by mass of nitrogen in NH₄NO₃, given relative atomic masses N = 14, H = 1 and O = 16.

Key term

In which unit is the concentration of a solution given when it is measured as a mass in a given volume?

Questions from this subtopic

Each one with the model answer underneath.

1
Define the relative formula mass of a compound.
Model answer
It is the sum of the relative atomic masses of all the atoms shown in the formula of the compound.
2
Calculate the relative formula mass of CO₂, given relative atomic masses C = 12 and O = 16.
Model answer
44.
3
Calculate the relative formula mass of H₂SO₄, given relative atomic masses H = 1, S = 32 and O = 16.
Model answer
98.
4
How does the total of the relative formula masses of the reactants compare with that of the products in a balanced equation?
Model answer
They are equal, provided each formula is counted the number of times shown by its balancing number.
5
For 2H₂ + O₂ → 2H₂O, show that the totals of relative formula mass are the same on both sides, given H = 1 and O = 16.
Model answer
The reactants total 2 × 2 + 32 = 36 and the products total 2 × 18 = 36, so both sides come to 36.
6
How is the percentage by mass of an element in a compound calculated?
Model answer
Divide the total relative atomic mass of that element in the formula by the relative formula mass of the compound, then multiply by 100.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Atomic Structure and the Periodic Table

Bonding, Structure, and the Properties of Matter

Chemical Analysis

Chemical Changes

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

J J .

ThomsonChadwickRutherford

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AMolecular size controls boiling point, viscosity and flammability.

BSmall molecules make gases and petrol that ignite easily.

CLarge molecules make thick liquids burned in furnaces and ships.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Base means any substance that neutralises an acid.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Quantitative Chemistry, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.