A-level Chemistry Tutor

Practical questions by PAG

At least 15% of the marks on the written papers are for practical skills: Module 1 of the specification. OCR groups the practical work into twelve Practical Activity Groups (PAGs). Below is what each involves, what the papers ask about it, and every past-paper question tagged to it. There are 274 practical question parts in total; see them all with their mark schemes.

The Practical Activity Groups

PAGActivityWhat the papers askQuestions
PAG 1Moles determinationMeasuring mass and gas volume to find a formula or a molar mass, for example water of crystallisation or the gas from a carbonate. Papers ask about gas syringes, loss of gas before the bung goes in, and heating to constant mass.27
PAG 2Acid–base titrationMaking a standard solution in a volumetric flask and titrating with a burette and pipette. Papers ask for concordant titres, the mean, percentage uncertainty, rinsing errors and the choice of indicator.68
PAG 3Enthalpy determinationMeasuring a temperature change to find an enthalpy change with q = mcΔT. Papers ask about heat loss, incomplete combustion, extrapolating a cooling curve and why the value differs from the data-book value.33
PAG 4Qualitative analysis of ionsTest-tube tests for ions: carbonate (acid), sulfate (barium ions), halides (silver nitrate then ammonia), ammonium (warm NaOH), and at A level the transition metal ions with NaOH and NH₃. Papers ask for the order of tests and the observations.28
PAG 5Synthesis of an organic liquidPreparing an organic liquid: heating under reflux, distillation, separating funnel, drying with an anhydrous salt, redistillation. Papers ask for labelled apparatus and the reason for each step.20
PAG 6Synthesis of an organic solidPreparing an organic solid: filtration under reduced pressure, recrystallisation from the minimum volume of hot solvent, melting point and thin-layer chromatography to check purity.16
PAG 7Qualitative analysis of organic functional groupsTest-tube tests for functional groups: bromine water (alkene), acidified dichromate (alcohols and aldehydes), 2,4-DNP and Tollens’ reagent (carbonyls), carbonates (carboxylic acids), silver nitrate in ethanol (haloalkanes), phenol tests.27
PAG 8Electrochemical cellsSetting up electrochemical cells and measuring cell potentials: half-cells, salt bridge, high-resistance voltmeter, platinum electrodes and standard conditions.6
PAG 9Rates of reaction – continuous monitoringFollowing a reaction continuously: gas volume, mass loss or colorimetry against time, then half-lives or gradients from the graph.26
PAG 10Rates of reaction – initial ratesInitial rates and clock reactions: how the initial rate changes with concentration, giving the orders and the rate constant.9
PAG 11pH measurementMeasuring pH with a meter or probe: calibration, titration curves, identifying solutions from their pH.1
PAG 12Research skillsResearch skills: finding, using and citing sources. It is assessed through the Practical Endorsement rather than the written papers.0

Descriptions written by the site from the specification (section 5g) and the mark schemes; being checked by our tutor. The Practical Endorsement itself is assessed by your teacher and reported separately as a pass.

PAG 1: Moles determination

Measuring mass and gas volume to find a formula or a molar mass, for example water of crystallisation or the gas from a carbonate. Papers ask about gas syringes, loss of gas before the bung goes in, and heating to constant mass.

PAG 2: Acid–base titration

Making a standard solution in a volumetric flask and titrating with a burette and pipette. Papers ask for concordant titres, the mean, percentage uncertainty, rinsing errors and the choice of indicator.

PAG 3: Enthalpy determination

Measuring a temperature change to find an enthalpy change with q = mcΔT. Papers ask about heat loss, incomplete combustion, extrapolating a cooling curve and why the value differs from the data-book value.

PAG 4: Qualitative analysis of ions

Test-tube tests for ions: carbonate (acid), sulfate (barium ions), halides (silver nitrate then ammonia), ammonium (warm NaOH), and at A level the transition metal ions with NaOH and NH₃. Papers ask for the order of tests and the observations.

PAG 5: Synthesis of an organic liquid

Preparing an organic liquid: heating under reflux, distillation, separating funnel, drying with an anhydrous salt, redistillation. Papers ask for labelled apparatus and the reason for each step.

PAG 6: Synthesis of an organic solid

Preparing an organic solid: filtration under reduced pressure, recrystallisation from the minimum volume of hot solvent, melting point and thin-layer chromatography to check purity.

PAG 7: Qualitative analysis of organic functional groups

Test-tube tests for functional groups: bromine water (alkene), acidified dichromate (alcohols and aldehydes), 2,4-DNP and Tollens’ reagent (carbonyls), carbonates (carboxylic acids), silver nitrate in ethanol (haloalkanes), phenol tests.

PAG 8: Electrochemical cells

Setting up electrochemical cells and measuring cell potentials: half-cells, salt bridge, high-resistance voltmeter, platinum electrodes and standard conditions.

PAG 9: Rates of reaction – continuous monitoring

Following a reaction continuously: gas volume, mass loss or colorimetry against time, then half-lives or gradients from the graph.

PAG 10: Rates of reaction – initial rates

Initial rates and clock reactions: how the initial rate changes with concentration, giving the orders and the rate constant.

PAG 11: pH measurement

Measuring pH with a meter or probe: calibration, titration curves, identifying solutions from their pH.

Planning, analysis and evaluation

Questions on experimental design, variables, anomalies, uncertainties and improvements that are not tied to one PAG.

21 questions

Work with an OCR chemistry tutor

Practical questions are 15% of the marks and the easiest to lose. A tutor can take you through each PAG.

Message us on WhatsApp About the tutoring
Prefer email? Send an enquiry

If you are under 18, please include a parent's contact details. Enquiries go to enquiries@chemistryaleveltutor.com and are deleted once handled. All tutoring is online.