Foundations in Chemistry | OCR A-Level Chemistry A (H432)

Foundations in Chemistry

284 questions
23 subtopics
Module 2: Foundations in chemistry
Component 01, Component 02 and Component 03

The quantitative and structural groundwork the rest of the course rests on: atomic structure and relative mass, writing formulae and equations, the mole and every calculation that follows from it, acids and titrations, oxidation numbers and redox, and electron configuration..

It covers atomic structure, isotopes and counting sub-atomic particles, relative isotopic, atomic, molecular and formula mass, predicting ionic charges and the common ions, writing formulae, balanced equations and ionic equations, the mole, molar mass and the Avogadro constant, empirical and molecular formulae, and hydrated salts, gas volumes, concentration and the ideal gas equation, stoichiometry, percentage yield and atom economy, apparatus, and why high atom economy matters, mathematical skills and measuring mass, volume and gas, acids, alkalis, dissociation and neutralisation, preparing a standard solution, carrying out a titration and its calculations, planning an experiment: variables, apparatus and recording results, uncertainty, percentage error, precision and accuracy, evaluating results: anomalies, conclusions, limitations and improvements, assigning oxidation numbers, roman numerals in names, and the chlorate and nitrate ions, oxidation, reduction and metals reacting with acids, redox equations and identifying what is oxidised, shells, orbitals and sub-shells, the order in which sub-shells fill and writing electron configurations for atoms and ions.

Sample questions from Foundations in Chemistry

Answer each one closed book first, then open the answer.

Atomic structure, isotopes and counting sub-atomic particles

Define the mass number of an atom.

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The total number of protons and neutrons in the nucleus.
Predicting ionic charges and the common ions

State the formula of the hydroxide ion.

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OH⁻
Empirical and molecular formulae, and hydrated salts

If dividing molar ratios by the smallest value gives non-whole numbers, what should you do?

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Multiply all values to obtain whole numbers.
Stoichiometry, percentage yield and atom economy

State the formula for calculating atom economy.

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Atom economy = (molecular mass of desired product / sum of molecular masses of all reactants) × 100.
Acids, alkalis, dissociation and neutralisation

What is the chemical formula of potassium hydroxide?

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KOH
Carrying out a titration and its calculations

Why is the balanced equation essential when performing titration calculations?

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It provides the mole ratio between the acid and base, which is needed to convert moles of one reactant to moles of the other
Evaluating results: anomalies, conclusions, limitations and improvements

What should a conclusion drawn from experimental results contain?

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A statement of the pattern or relationship the data show, supported by values from the results and explained using chemical ideas.
Roman numerals in names, and the chlorate and nitrate ions

State the formula of chlorate(V) and the oxidation number of chlorine it contains.

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ClO₃⁻; chlorine has oxidation number +5

The 23 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Atomic structure, isotopes and counting sub-atomic particles	Recall questions on protons, neutrons and electrons, what makes two atoms isotopes, and counting the particles in an atom or an ion from A, Z and the charge.	14
Relative isotopic, atomic, molecular and formula mass	Recall questions on the definitions of relative isotopic and relative atomic mass, the carbon-12 standard, and the weighted-mean calculation from mass spectrometry data.	14
Predicting ionic charges and the common ions	Recall questions on deducing an ionic charge from the group, and on the formulae and charges of nitrate, carbonate, sulfate, hydroxide, ammonium, zinc and silver.	13
Writing formulae, balanced equations and ionic equations	Recall questions on building an ionic formula from the charges, what a balanced equation requires, state symbols, spectator ions and balancing charge as well as atoms.	13
The mole, molar mass and the Avogadro constant	Recall questions on amount of substance and its unit, the Avogadro constant, molar mass, and finding an amount from a mass or a number of particles.	11
Empirical and molecular formulae, and hydrated salts	Recall questions on finding an empirical formula from percentage composition, scaling it to a molecular formula, and the water of crystallisation in a hydrated salt.	15
Gas volumes, concentration and the ideal gas equation	Recall questions on molar gas volume at RTP, concentration in mol dm⁻³ and g dm⁻³, and using pV = nRT with SI units throughout.	13
Stoichiometry, percentage yield and atom economy	Recall questions on the steps of a reacting-mass calculation, theoretical and percentage yield, and calculating atom economy.	10
Apparatus, and why high atom economy matters	Recall questions on the apparatus used to measure mass, solution volume and gas volume, and on the waste, resource and cost arguments for high atom economy.	11
Mathematical skills and measuring mass, volume and gas	Recall questions on standard form, rearranging an equation for an unknown, estimating before calculating, and choosing apparatus of the right precision.	14
Acids, alkalis, dissociation and neutralisation	Recall questions on the formulae of the common acids and alkalis, strong against weak dissociation, the ionic equation for neutralisation, and the products with carbonates and metal oxides.	16
Preparing a standard solution	Recall questions on weighing the solute, transferring it quantitatively to a volumetric flask, making up to the mark and mixing thoroughly.	10
Carrying out a titration and its calculations	Recall questions on rinsing and filling the burette, the indicator and the end point, concordant titres, and using the mole ratio to find a concentration.	10
Planning an experiment: variables, apparatus and recording results	Recall questions on independent, dependent and control variables, planning an investigation and choosing apparatus, judging whether a method suits its aim, trial titrations, and recording raw results to the right precision.	12
Uncertainty, percentage error, precision and accuracy	Recall questions on measurement uncertainty for burettes and balances, the uncertainty in a titre, calculating percentage uncertainty and percentage error, accuracy and precision, and random and systematic errors.	14
Evaluating results: anomalies, conclusions, limitations and improvements	Recall questions on identifying and excluding anomalous results, drawing and judging conclusions, repeatable and reproducible results, and the limitations and improvements of common experimental procedures.	12
Assigning oxidation numbers	Recall questions on the rules for elements, monatomic ions, oxygen, hydrogen and fluorine, and on solving for an unknown oxidation number in a compound or ion.	14
Roman numerals in names, and the chlorate and nitrate ions	Recall questions on what a Roman numeral tells you, the iron(II) and iron(III) ions, and the formulae of chlorate(I), chlorate(III) and chlorate(V).	8
Oxidation, reduction and metals reacting with acids	Recall questions on oxidation and reduction as electron transfer, oxidising and reducing agents, and the products when magnesium, aluminium, iron and zinc react with dilute acids.	12
Redox equations and identifying what is oxidised	Recall questions on assigning oxidation numbers across an equation, identifying the species oxidised and reduced, and why the total increase equals the total decrease.	15
Shells, orbitals and sub-shells	Recall questions on shell capacities, what an atomic orbital is, the shapes of s and p orbitals, and the number of orbitals and electrons in each sub-shell.	14
The order in which sub-shells fill	Recall questions on the filling order from 1s to 4p, why 4s fills before 3d, and how electrons occupy orbitals of equal energy.	10
Writing electron configurations for atoms and ions	Recall questions on electrons-in-boxes and sub-shell notation, and on writing the configuration of a neutral atom, a cation and an anion.	9

Foundations in Chemistry is 284 of the 1,913 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.