Edexcel A-Level Chemistry Revision
Explore Edexcel A-Level Chemistry revision topics. Check the official specification for complete requirements for your exam year and route.
Qualification code: 9CH0
Course details
Assessment The assessment includes Paper 3; see the official specification for the full structure.
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Reviewed course guidance
Revision points, with the explanation beside them
Open a point to read what to know, how to use it in an assessment, a plain-language explanation and a self-check. Answers stay hidden until you choose to reveal them.
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Topic group
Reviewed requirements
- Core
Open revision guidance
What to know
- Multiply each supplied relative atomic mass by its subscript and add the contributions. Keep the stated precision and compare the resulting accurate mass with the candidate compounds.
What to do in an assessment
- Write the atom count for each element, multiply by its supplied relative atomic mass, add without premature rounding, then compare the result at four decimal places with the candidate molecular-ion/compound data to identify the match.
In plain language
Accurate mass is the sum of the atoms in a formula. The resulting value can be compared with candidate data to identify which compound matches the measured molecular mass.
Self-check
Using Ar(C)=12.0000, Ar(H)=1.0078 and Ar(O)=15.9949, calculate Mr for C₃H₈O and identify the match between candidate masses 60.0573 and 76.0522.
Show the answer
Mr(C₃H₈O)=3(12.0000)+8(1.0078)+15.9949=60.0573, so the 60.0573 candidate matches.
- Core
Open revision guidance
What to know
- Each distinct carbon environment produces a distinct ¹³C NMR signal. Use supplied chemical-shift (δ) values to decide which carbon atoms are in equivalent environments and justify the peak count.
What to do in an assessment
- Mark each carbon in the structure, group equivalent environments, then count those groups. Use the supplied δ values to support your assignment rather than assuming every carbon gives a separate peak.
In plain language
The spectrum counts different carbon surroundings, not atoms one by one. Equivalent carbons share an environment and signal.
Self-check
How many ¹³C signals are expected for CH₃CH₂OH, with two carbon environments?
Show the answer
Two signals: one for the CH₃ environment and one for CH₂.
- Core
Scope: Core · Topic 19B point 5(ii)–(iii): relate relative peak areas to relative proton numbers and deduce splitting by the (n+1) rule
Open revision guidance
What to know
- Relative peak areas or ratio numbers show the relative number of ¹H atoms in different environments. For adjacent non-equivalent protons, apply the specified (n+1) rule to deduce splitting.
What to do in an assessment
- Use integration ratios to compare proton counts. Then count n equivalent adjacent protons and predict n+1 lines; use the rule only for the stated adjacent, non-equivalent environments.
In plain language
Integration compares the numbers of hydrogens represented by signals; splitting shows how neighbouring protons divide a signal into lines.
Self-check
A proton signal is split by two equivalent neighbouring hydrogens. How many lines does the (n+1) rule predict?
Show the answer
Three lines: n+1 = 2+1 = 3.
- Core
Scope: Core · Topic 19C Chromatography, point 7: calculate Rf values from one-way chromatograms
Open revision guidance
What to know
- Rf is the distance travelled by the substance divided by the distance travelled by the solvent front, with both distances measured from the same baseline. It has no unit.
What to do in an assessment
- Measure both distances from the baseline in the direction of travel, use the same units, divide spot distance by solvent-front distance and report the ratio without units.
In plain language
Rf compares how far a spot moved with how far the solvent moved. It is a unitless ratio.
Self-check
A spot moves 3.0 cm while the solvent front moves 8.0 cm. What is Rf?
Show the answer
Rf = 3.0 ÷ 8.0 = 0.375.
Earlier topic checklist
These earlier topic ticks are separate from the reviewed points above and do not count towards that progress.
Chemistry topic list
This is a topic overview, not a complete specification checklist. Check the official course for all assessed content, options and your exam year.
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These ticks keep your earlier topic checklist. They do not count towards the new reviewed requirements above. Its numbering may be internal; use the linked references above for the exact reviewed source requirements.
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