IB Chemistry IA ideas: 25 research questions with ranges, methods and safety notes

A workable IB Chemistry IA idea changes one variable across at least five levels and measures a response you can turn into a chemical quantity: a rate constant, an order, an activation energy, an equilibrium constant, an enthalpy change or a concentration. Below are 25 such ideas as full research questions, each with its method and the trap that most often costs marks. Change the system, range or context to make one your own.

Every idea needs a risk assessment agreed with your teacher; hazards below are noted only where specific to the idea. To sharpen your own question, see how to write an IA research question.

Which kinetics investigations work best (Reactivity 2.2)?

1. Temperature and the thiosulfate–acid reaction

RQ: How does temperature (20, 30, 40, 50 and 60 °C) affect the rate of reaction between 0.10 mol dm⁻³ sodium thiosulfate and 1.0 mol dm⁻³ hydrochloric acid, and what is the activation energy?

• Method: time to a fixed cloudiness, ideally by light sensor. Rate ∝ 1/t; the gradient of ln(1/t) against 1/T is −E_a/R.
• Trap: the mixture cools once mixed, so preheat both solutions and use the mean of start and end temperatures. Sulfur dioxide is released: small volumes, good ventilation, extra care with asthma.

2. Order with respect to iodide (iodine clock)

RQ: How does iodide concentration (0.020, 0.040, 0.060, 0.080 and 0.100 mol dm⁻³) affect the initial rate of the acidified hydrogen peroxide–iodide reaction, and what is the order with respect to iodide?

• Method: fixed small amounts of thiosulfate and starch; time until blue-black appears. The gradient of log(rate) against log[I⁻] is the order.
• Trap: keep the total volume constant with water, or every concentration changes at once. Take the order from the gradient with its uncertainty, not the graph's shape.

3. Acid concentration and magnesium

RQ: How does hydrochloric acid concentration (0.25, 0.50, 0.75, 1.00, 1.50 and 2.00 mol dm⁻³, 50 cm³) affect the initial rate of hydrogen production from 0.040 g of magnesium ribbon, measured with a gas syringe over the first 20 s?

• Method: initial rate from the first linear part; 0.040 g of magnesium gives about 40 cm³ of hydrogen. Clean off the oxide with emery paper.
• Trap: the reaction heats itself, more so in concentrated acid, so part of the rate rise is a temperature effect. Record the temperature rise.

4. Temperature and the fading of crystal violet

RQ: How does temperature (15, 20, 25, 30, 35 and 40 °C) affect the rate constant for the reaction of crystal violet (about 1 × 10⁻⁵ mol dm⁻³) with excess sodium hydroxide (0.020 mol dm⁻³), followed by absorbance at about 590 nm?

• Method: excess hydroxide makes it pseudo-first order: ln A against time has gradient −k′; then an Arrhenius plot. Crystal violet is a suspected carcinogen: gloves, dilute solutions only.
• Trap: the cuvette drifts towards room temperature. Use a thermostatted holder or short runs, and check ln A is linear before trusting the gradient.

What equilibrium IAs can you run in a school lab (Reactivity 2.3)?

5. Temperature and K_c for iron(III) thiocyanate

RQ: How does temperature (10, 20, 30, 40 and 50 °C) affect the equilibrium constant K_c for Fe³⁺(aq) + SCN⁻(aq) ⇌ [FeSCN]²⁺(aq), determined by colorimetry at about 450 nm?

• Method: calibrate with Fe³⁺ in large excess, then an ICE table per mixture; acidify with dilute nitric acid to stop Fe³⁺ hydrolysing. The gradient of ln K against 1/T is −ΔH°/R (beyond the syllabus, but it follows from ΔG° = −RT ln K).
• Trap: ΔH is small, so K changes only modestly; your uncertainties must be smaller than that change. Keep thiocyanate away from concentrated acids (toxic gas).

6. Is K_c for esterification really constant?

RQ: Does K_c for CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O stay constant at room temperature when the initial ethanol : ethanoic acid mole ratio is 1:4, 1:2, 1:1, 2:1 or 4:1, determined by titrating the remaining acid after one week?

• Method: sealed tubes with a fixed volume of acid catalyst; titrate after five and seven days to confirm equilibrium. Published values are around 4.
• Trap: titrate a blank of the catalyst alone and subtract it, and include any water present at the start (from the catalyst solution or the ethanol) in the ICE table.

7. Temperature and the solubility of calcium hydroxide

RQ: How does temperature (10, 20, 30, 40, 50 and 60 °C) affect the solubility of calcium hydroxide, determined by titrating the filtered saturated solution with 0.0500 mol dm⁻³ hydrochloric acid?

• Method: stir excess solid for 30 minutes at each temperature, filter, titrate (25.0 cm³ at 20 °C needs about 23 cm³). Solubility falls as temperature rises because dissolving is exothermic, a good Le Chatelier discussion; K_sp = 4s³ extends it. Goggles throughout.
• Trap: a hot solution that cools while touching the solid dissolves more, so filter fast through a pre-warmed funnel. Cover solutions: air CO₂ precipitates calcium carbonate.

Which energetics ideas avoid the heat-loss problem?

Calorimetry (Reactivity 1.1–1.3) loses heat, so build the analysis around trends that survive low absolute values.

8. Chain length and enthalpy of combustion of alcohols

RQ: How does the number of carbon atoms in a straight-chain primary alcohol (methanol to pentan-1-ol) affect the enthalpy of combustion measured by spirit-burner calorimetry, compared with published values per CH₂ group?

• Method: burner mass loss and temperature rise of 100 cm³ of water in a copper can; ΔH_c = −mcΔT/n. Fix flame-to-can distance and draught shielding. Methanol is toxic.
• Trap: published values become more exothermic by about 650 kJ mol⁻¹ per CH₂, but losing a constant fraction of heat shrinks your gradient by that fraction too. So test the pattern: is your trend linear, and is your value as a fraction of the published one similar for every alcohol? If so, the error is systematic.

9. Concentration and the temperature rise for zinc and copper(II) sulfate

RQ: How does copper(II) sulfate concentration (0.10, 0.20, 0.30, 0.40 and 0.50 mol dm⁻³, 50 cm³, with 3 g of zinc powder) affect the maximum temperature rise, and what enthalpy change does the gradient give?

• Method: lidded insulated cup; extrapolate the cooling curve back to the moment of mixing. Treating the solution as water, ΔH (kJ mol⁻¹) = −4.18 × gradient of ΔT against concentration. Expect about 26 °C at 0.50 mol dm⁻³.
• Trap: bigger rises lose more heat, so the line may curve; analyse that. Zinc stays in excess (0.025 mol Cu²⁺ needs about 1.6 g).

10. Hess's law and enthalpies of solution of group 1 halides

RQ: How do measured enthalpies of solution of the chlorides, bromides and iodides of lithium, sodium and potassium vary with ionic radius, and how do they compare with Hess's law values from lattice and hydration enthalpies?

• Method: about 0.05 mol of each dry salt in 50 cm³ of water in an insulated cup; Hess cycle from data-booklet or published values.
• Trap: the sodium salts change the temperature by under 2 °C (sodium bromide by about 0.1 °C), so expect big percentage uncertainties. The Hess value is a small difference between two large numbers, so compare trends.

What electrochemistry ideas are realistic?

11. Concentration and cell potential

RQ: How does copper(II) ion concentration (0.001, 0.003, 0.01, 0.03, 0.1, 0.3 and 1.0 mol dm⁻³) affect the EMF of a Zn | Zn²⁺ (1.0 mol dm⁻³) || Cu²⁺ | Cu cell at 25 °C, and does the trend match the Nernst prediction?

• Method: high-resistance voltmeter, fresh salt bridge each run; plot EMF against log₁₀[Cu²⁺]. For this two-electron couple at 298 K, the Nernst equation (citable, though beyond the syllabus) predicts 2.303RT/2F ≈ 0.030 V per tenfold change.
• Trap: EMF depends on log concentration, hence levels in factors of about 3. Ions behave less ideally at high concentration, so expect and discuss deviation there.

12. Current and the Faraday constant

RQ: How does current (0.20, 0.40, 0.60, 0.80 and 1.00 A) affect the mass of copper deposited on a copper cathode in 20.0 minutes of electrolysis of 0.5 mol dm⁻³ copper(II) sulfate, and what value of the Faraday constant does the gradient give?

• Method: constant current; weigh the clean, dry cathode to 0.001 g. Since m = ItM/2F, F = tM/(2 × gradient). Expect about 0.08 g at 0.20 A and 0.40 g at 1.00 A.
• Trap: at high current the deposit can turn powdery and flake off when rinsed, lowering exactly the points that set the gradient. Rinse gently.

13. Salt concentration and the rate of rusting

RQ: How does sodium chloride concentration (0, 0.5, 1.0, 2.0, 3.5 and 5.0% w/v) affect the initial rate of oxygen consumption by 1.0 g of rusting steel wool, measured as the rise of water in an inverted measuring cylinder over 6 hours?

• Method: wet, degreased steel wool at the top of a cylinder standing in water; read the level every 30 minutes, with an empty control cylinder for temperature and pressure changes.
• Trap: air is about a fifth oxygen, so the level plateaus; use the initial rate. More salt is not always faster: oxygen is less soluble in saltier water, and classic studies of iron in aerated salt solutions find a peak near 3% NaCl.

Which titration investigations have a real variable?

14. Heating time and vitamin C in orange juice

RQ: How does heating time at 90 °C (0, 5, 10, 15, 20 and 30 minutes) affect the ascorbic acid concentration of freshly squeezed orange juice, determined by titration with 0.0050 mol dm⁻³ iodine using starch indicator?

• Method: ascorbic acid reacts with iodine 1:1; standardise the iodine against known ascorbic acid on the day, and top heated samples up to their starting mass.
• Trap: juice oxidises in air, so titrate every sample at the same interval. Other reducing substances react with iodine too, slightly inflating the result.

15. Temperature and dissolved oxygen (Winkler titration)

RQ: How does water temperature (5, 10, 15, 20, 25, 30 and 35 °C) affect the dissolved oxygen concentration (mg dm⁻³) of air-saturated deionised water, determined by Winkler titration and compared with published solubility tables?

• Method: aerate at temperature, fill a stoppered bottle, fix with manganese(II) sulfate and alkaline iodide, acidify, titrate the iodine with thiosulfate. The alkaline iodide and concentrated sulfuric acid are corrosive. Skip the azide version of the reagent: it is meant for river water, and sodium azide is highly toxic.
• Trap: air oxygen enters at every step. Fill bottles from the bottom until they overflow, and fix immediately.

16. Boiling time and water hardness

RQ: How does boiling time (0, 2, 5, 10, 15 and 20 minutes) affect the total hardness of one named local tap water, measured as mg dm⁻³ CaCO₃ by EDTA titration with Eriochrome Black T at pH 10?

• Method: boil, cool, make up to the starting mass, filter, titrate. Boiling removes temporary hardness (calcium hydrogencarbonate → calcium carbonate) but not permanent hardness, so expect a fall to a plateau. Ammonia buffer goes in a fume cupboard.
• Trap: without the make-up step, evaporation hides the effect. Soft tap water gives titres too small to use.

What acid–base and buffer ideas work?

These need a pH probe calibrated with two buffers that bracket your range (Reactivity 3.1).

17. Buffer ratio and pH

RQ: How does the ratio [CH₃COO⁻] : [CH₃COOH] (0.10, 0.25, 0.50, 1.0, 2.0, 4.0 and 10) affect the pH of an ethanoate buffer, and how closely does pH follow pK_a + log₁₀(ratio)?

• Method: mix 0.10 mol dm⁻³ acid and sodium ethanoate to 50.0 cm³ (ratio 0.10 is 4.55 cm³ of salt with 45.45 cm³ of acid); plot pH against log₁₀(ratio). The intercept is your pK_a.
• Trap: non-ideal behaviour usually puts the measured pK_a slightly below the tabulated 4.76; discuss it.

18. Concentration and buffer capacity

RQ: How does the total concentration of a 1:1 ethanoic acid–sodium ethanoate buffer (0.020, 0.040, 0.080, 0.12, 0.16 and 0.20 mol dm⁻³) affect the volume of 0.10 mol dm⁻³ sodium hydroxide needed to raise the pH of 50.0 cm³ by 1.0 unit?

• Method: log pH after each addition from a burette. Henderson–Hasselbalch predicts a straight line through the origin: about 4.1 cm³ at 0.020 mol dm⁻³, about 41 cm³ at 0.20 mol dm⁻³.
• Trap: do not stop by eye; plot pH against volume and interpolate the volume at exactly +1.0.

19. Chain length and pK_a of carboxylic acids

RQ: How does the number of carbon atoms in a straight-chain carboxylic acid (methanoic to pentanoic acid) affect its pK_a, determined from the pH at the half-equivalence point of a titration with 0.10 mol dm⁻³ sodium hydroxide?

• Method: full pH curve, equivalence point from the steepest gradient, pH read at half that volume. Butanoic and pentanoic acids smell strongly; use a fume cupboard.
• Trap: published pK_a values rise from about 3.75 (methanoic) to 4.76 (ethanoic), then sit between 4.8 and 4.9 from propanoic to pentanoic, differences within a school probe's uncertainty. "No difference detectable" may be the honest, creditable conclusion.

How do you use colorimetry and Beer–Lambert well?

Beer–Lambert (A = εcl) holds only at low absorbance: always calibrate, use the wavelength of strongest absorption, and dilute into the straight part. See graphs for the IA.

20. Hypochlorite concentration and dye bleaching

RQ: How does sodium hypochlorite concentration (five concentrations, all in large excess) affect the rate constant for the fading of the food dye E133 (brilliant blue FCF) at 25 °C, measured at about 630 nm, and what is the order in hypochlorite?

• Method: ln A against time gives −k′ for each run; log k′ against log[OCl⁻] gives the order. Hypochlorite plus acid releases chlorine.
• Trap: hypochlorite weakens on standing; standardise it by iodometric titration on the day.

21. Formula of a complex by continuous variation

RQ: What is the iron(III) : salicylate ratio in the violet complex formed at pH about 2.5, determined by continuous variation (salicylate mole fraction 0.1 to 0.9, constant total concentration) at about 530 nm?

• Method: mix equal-concentration stocks in varying proportions to one total volume; absorbance peaks at the mole fraction matching the formula. Locate it as the intersection of two fitted lines.
• Trap: one pipetting slip moves the peak. Keep pH fixed, because other complexes form at higher pH.

Which organic and materials ideas are feasible?

These need a fume cupboard, a heating mantle or water bath instead of a flame, and planned waste disposal.

22. Catalyst amount and ester yield

RQ: How does the volume of concentrated sulfuric acid catalyst (0.20, 0.40, 0.60, 0.80 and 1.00 cm³) affect the conversion of 0.10 mol each of ethanol and ethanoic acid to ethyl ethanoate after 30 minutes' reflux, determined by titrating the remaining acid?

• Method: reflux, cool, dilute, titrate with standard sodium hydroxide, subtract the catalyst's share, calculate percentage conversion. Add the concentrated acid slowly, with cooling, under supervision.
• Trap: 1.00 cm³ of concentrated sulfuric acid supplies about 0.037 mol H⁺, similar to the ethanoic acid left, so weigh the catalyst and titrate a matching blank. A catalyst does not change K_c, but this one also absorbs water; discuss which effect your data show.

23. Temperature and ester hydrolysis followed by conductivity

RQ: How does temperature (20, 25, 30, 35 and 40 °C) affect the rate constant for the alkaline hydrolysis of ethyl ethanoate (0.020 mol dm⁻³ ester and 0.020 mol dm⁻³ sodium hydroxide), followed by conductivity, and what is the activation energy?

• Method: conductivity falls as OH⁻ is replaced by slower ethanoate ions. Convert readings to [OH⁻] using the start and end values; with equal starting concentrations, 1/[OH⁻] against time has gradient k.
• Trap: conductivity rises about 2% per °C, so drift looks like reaction. Hold the bath within ±0.2 °C.

24. The halogen and hydrolysis of halogenoalkanes

RQ: How does the halogen (chlorine, bromine, iodine) in 1-halobutanes affect the rate of hydrolysis with aqueous silver nitrate in ethanol at 30, 35, 40, 45 and 50 °C, and do the activation energies follow C–X bond enthalpies?

• Method: time to a fixed cloudiness with a light sensor; an Arrhenius plot per compound.
• Trap: three halogens alone give only three points, hence the temperatures. The precipitates differ in colour, so cloudiness by eye is not comparable. Pilot the slow chloro compound first.

25. Cross-linker concentration and the viscosity of PVA gel

RQ: How does sodium tetraborate concentration (0.5, 1.0, 2.0, 3.0 and 4.0% w/v, 5 cm³ added to 50 cm³ of 4% poly(vinyl alcohol)) affect gel viscosity, measured as the time for a steel ball to fall 10 cm through it?

• Method: borate cross-links OH groups on neighbouring chains (Structure 2.4); test each gel at a fixed time after mixing. Borax is classified in the EU and UK as toxic to reproduction and some schools restrict it: check first, wear gloves.
• Trap: the gel is non-Newtonian, so a falling-ball time is an apparent viscosity for that ball only; say so.

How do you check that a Chemistry IA idea is feasible?

1. Time: multiply levels × repeats × time per run; the IA has about 10 hours in the course plan, writing included.
2. Effect versus uncertainty: in a pilot, is the difference between the extreme levels clearly bigger than the spread of repeats? See uncertainties in the IA.
3. A processed quantity: does the data become k, E_a, an order, K_c, ΔH, F or pK_a?
4. A comparison: is there a published value or theory to judge your result against?
5. Safety and waste: is every chemical allowed in your school, with a disposal route?

An idea that passes all five can support every criterion in the science IA criteria.