OCR A-Level Chemistry data sheet: A complete breakdown

The OCR A-Level Chemistry A (H432) data sheet is the most-reused document across the three written papers. A common mistake is to describe it as 'just the periodic table'. It isn't: the booklet has five distinct sections, and only one of them is the periodic table. The others are a short list of constants, an infrared absorption table, a carbon-13 NMR chemical-shift table, and a proton NMR chemical-shift table. Each one is designed to let OCR ask about calculations and spectra without expecting you to memorise reference values. All are set out in the OCR Chemistry A specification.

This guide covers OCR A (H432). If you're on OCR Chemistry B Salters (H433), the data sheet is a different document with some different values, so check your spec code before using this. The piece below walks through every section, flags where each value shows up on the exam, and lists the formulae that are NOT on the sheet so you know what you still need to memorise.

The first page lists the handful of physical constants OCR uses most often. The list is short, which is deliberate: these are the values that appear in enough different question types that printing them saves time and dodges copy-and-remember errors.

A few of these catch students out. Molar gas volume is quoted at room temperature and pressure (RTP), so for calculations at STP or non-standard conditions you need the ideal-gas equation (pV = nRT) instead. The Arrhenius equation is given in both exponential and logarithmic forms, which is a hint that OCR will set questions asking you to plot ln k against 1/T and extract E_a from the gradient. The ionic product of water K_w is on the sheet with its value at 298 K, so pH-of-pure-water-at-25°C questions are a quick lookup rather than a memory test.

The second section is the IR table. It lists common bonds in organic molecules with the wavenumber range at which each one absorbs. You'll use this every time a question asks you to identify a functional group from an IR spectrum.

Three of these are worth internalising even though they're on the sheet, because they come up in nearly every IR question. The C=O band near 1700 cm^-1 is the diagnostic signal for carbonyl groups and is where you look first. The broad O-H band at 2500-3300 cm^-1 pairs with that C=O to confirm a carboxylic acid rather than an aldehyde or ketone. The C-H region around 3000 cm^-1 shows up on practically every organic spectrum but is rarely diagnostic on its own. Students who hunt for peaks top-down (highest wavenumber first) tend to be slower than students who go straight to the C=O region, so train the ordered sweep.

Section 3 is the ¹³C NMR shift chart. It covers the chemical-shift ranges (relative to TMS, in ppm) for the common environments you meet at A-Level: alkyl carbons, carbons bonded to electronegative atoms, aromatic carbons, and carbonyl carbons.

The practical workflow in an exam question is: count the number of distinct peaks (number of unique carbon environments), look at where each one sits on the shift scale, then build up the molecule. Aromatic carbons sit between 100 and 150 ppm. Carbonyls sit at roughly 160 to 220 ppm (acid-type groups around 160-185, aldehydes and ketones around 190-220). Carbons bonded to oxygen sit at about 50-90 ppm, and carbons bonded to halogens or nitrogen a little lower, at about 30-70 ppm. Plain alkyl carbons sit at 5-55 ppm.

OCR flags on the sheet that chemical shifts vary with solvent, concentration and substituents. The ranges are approximate rather than exact, so don't be surprised if a shift sits a few ppm outside the quoted band.

Section 4 is the ¹H NMR shift chart. It gives shift ranges only: splitting patterns (the n+1 rule) and relative peak areas aren't printed, so you need to know how to use them from memory. The ranges cover alkyl protons (0.5-2 ppm), protons alpha to carbonyls or electronegative atoms (2-5 ppm), aromatic protons (6.5-8 ppm) and acidic O-H and N-H protons (variable).

OCR notes on the sheet that OH and NH signals are 'very variable and often broad', and that these peaks 'are not usually seen as split peaks'. This is a crucial detail: students who try to apply n+1 splitting rules to an OH signal end up predicting a splitting pattern that just isn't there, because the proton exchanges too fast between molecules to couple consistently. Treat OH and NH shifts as broad singlets rather than part of the n+1 analysis.

The final page is a full periodic table. Each element shows the symbol, name, atomic (proton) number and relative atomic mass. The lanthanides and actinides sit in the standard pull-out rows underneath the main body.

Use the printed A_r values for every mole calculation. OCR's mark schemes are worked from the printed values, so always use those rather than a value you've memorised.

The periodic table is also where you work out electron configurations on the fly. Block (s, p, d, f) tells you which subshell is being filled, period tells you the principal energy level, and group tells you the number of valence electrons. You can build up a configuration like [Ar] 3d⁶ 4s² for iron by reading the table rather than remembering it cold.

Trend questions hinge on the table too. Across a period, atomic radius decreases and first ionisation energy generally rises. Down a group, atomic radius increases and first ionisation energy falls. Group 2, Group 7, and Period 3 trend questions all route back to the periodic-table layout.

The data sheet is a reference booklet, not a full formula sheet. A long list of relationships you'll need in the exam are not on it, and you'll need to recall them from memory.

First, the mole relationships: n = m / M_r, n = c × V (with V in dm³), n = N / N_A. These are the daily-driver equations and OCR doesn't print them. The ideal-gas equation pV = nRT is also not on the sheet, though R is.

Second, the pH relationships. pH = -log₁₀[H⁺], K_a = [H⁺][A^-] / [HA], pK_a = -log₁₀ K_a, and the Henderson-Hasselbalch-style buffer relationship pH = pK_a + log([A^-] / [HA]). K_w is on the sheet, but the pH formula that uses it is not.

Third, thermochemistry. Hess's law cycles, ΔG = ΔH - TΔS, bond-enthalpy summations, enthalpy of combustion versus formation. These all need recall. The one calorimetry relationship you'll use (q = mcΔT) is also not on the sheet, though c for water is.

Fourth, electrochemistry. E^⦵_cell = E^⦵_reduction - E^⦵_oxidation, and how to use electrode potentials to predict feasibility. The cell-potential relationship is not on the data sheet. (Electrolysis calculations using Q = It and the Faraday constant aren't part of OCR A, so you won't need them for H432.)

Fifth, rates. The rate equation (rate = k [A]^m [B]ⁿ), half-life relationships for first-order reactions, and the gradient-based methods for extracting order from a concentration-time graph. The Arrhenius equation is on the sheet; the rate equation is not.

Sixth, organic chemistry. Percentage yield, atom economy, degree of unsaturation, structural-formula conventions. None of these are on the sheet, though the IR and NMR reference tables are.

Having every reference value in front of you isn't the same as being able to use them under exam pressure. Our wider A-Level revision techniques guide covers the general approach, but a few data-sheet-specific habits make a real difference.

Download the OCR Chemistry A data sheet from the OCR Chemistry A qualifications page and keep a printed copy in your folder. Use it on every past paper. Students who have never seen the layout before waste real time flipping through sections looking for a value. Students who've practised with it go straight to the IR table or the shift chart.

For each section, time yourself answering a question that uses it. One IR identification, one ¹³C spectrum, one ¹H spectrum, one Arrhenius-plot gradient question, one pH-of-water-type K_w question. If any of them take you more than a couple of minutes with the data sheet in front of you, that's your weakest link.

For the formulae that are NOT on the sheet, build a one-page recall card. Mole relationships, pH relationships, thermochemistry, electrochemistry, rates, yield and atom economy. Write it out from memory every weekend during the revision run-up. The absence of these from the data sheet is a deliberate choice: OCR expects pure recall, so you need to drill them.

Finally, cross-check against mark schemes. OCR mark schemes are tight on significant figures and on which value you took from the sheet. If a calculation comes out slightly different from the mark scheme, your first check is whether you used the printed A_r rather than a memorised one.

Cognito's OCR A-Level Chemistry course teaches every topic that leans on the data sheet, with short video lessons on IR and NMR interpretation, pH calculations, Arrhenius-equation plots, and electron configurations off the periodic table. If you also want to compare how different boards structure their data booklets, our guides to the AQA A-Level Chemistry data sheet and the Edexcel A-Level Chemistry data sheet walk through the differences in detail.