12 IB Chemistry IA ideas

How does the concentration of sodium thiosulfate (0.05–0.25 mol dm⁻³) affect the rate of its reaction with dilute HCl, measured by the disappearing-cross method?

Difficulty:

easy

Time:

1 week

Equipment:

school lab

Analysis:

Order of reaction from 1/time

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

Cross drawn inconsistently

Variables · IV: [Na₂S₂O₃]. DV: 1/time for the cross to vanish. Control: [HCl], total volume, temperature, same observer.

Note · Plot rate against concentration to find the order with respect to thiosulfate.

How does temperature (20–60 °C) affect the rate of the iodine-clock reaction, and what activation energy does an Arrhenius plot give?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

Arrhenius / rate vs T

Feasibility:

4/5

Overused:

Less common

Biggest trap:

Temperature drift in water bath

Variables · IV: temperature. DV: rate = 1/time. Process: ln k vs 1/T. Control: all concentrations, volume.

Note · A strong IA — the analysis produces Eₐ with an uncertainty, not just a trend.

How does the number of carbon atoms in a straight-chain alcohol (C1–C5) affect its molar enthalpy of combustion?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

Gradient from calibration curve

Feasibility:

4/5

Overused:

Less common

Biggest trap:

Blank not zeroed on colorimeter

Variables · IV: alcohol chain length. DV: ΔH_c from calorimetry (kJ mol⁻¹). Control: calorimeter, mass of water, distance to wick, draught shielding.

Note · Compare to Data Booklet values and discuss the systematic heat-loss error quantitatively.

How does the concentration of ethanoic acid in commercial vinegars affect the volume of NaOH needed to neutralise a fixed sample, and how do brands compare?

Difficulty:

easy

Time:

1 week

Equipment:

school lab

Analysis:

t-test on titre volumes

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

Endpoint overshoot

Variables · IV: vinegar brand/sample. DV: mean titre → [CH₃COOH]. Control: NaOH concentration, indicator, sample volume.

How does the surface area of calcium carbonate (chips vs granules vs powder) affect the initial rate of CO₂ loss when reacted with excess HCl?

Difficulty:

hard

Time:

multi-week

Equipment:

school lab

Analysis:

Hess cycle / ΔH calculation

Feasibility:

3/5

Overused:

Less common

Biggest trap:

Heat loss to calorimeter

Variables · IV: CaCO₃ particle size (measured, not just labelled). DV: mass loss gradient in the first 30 s. Control: mass of CaCO₃, [HCl], volume, temperature.

How does the concentration of a copper(II) sulfate solution affect its absorbance at 620 nm, and how accurately can an unknown be determined from the calibration line?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

Rate vs concentration

Feasibility:

4/5

Overused:

Often seen

Biggest trap:

Gas syringe leaks

Variables · IV: [CuSO₄] (serial dilutions). DV: absorbance. Control: path length, wavelength, blank, temperature.

Note · Beer–Lambert IA — quote the unknown with a confidence interval from the line of best fit.

How does the concentration of a weak acid (ethanoic, propanoic, citric at matched molarity) affect the measured pH, and what Ka does each give?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

pH vs rate

Feasibility:

4/5

Overused:

Less common

Biggest trap:

Buffer capacity exceeded

Variables · IV: acid identity at fixed [H⁺-donor]. DV: pH → Ka. Control: temperature, calibration of the probe, total volume.

How does the mass of anhydrous CaCl₂ dissolved in a fixed volume of water affect the temperature change, and what is the molar enthalpy of solution?

Difficulty:

easy

Time:

1 week

Equipment:

basic

Analysis:

Linear regression

Feasibility:

5/5

Overused:

Less common

Biggest trap:

Electrode not calibrated

Variables · IV: mass of CaCl₂. DV: ΔT → ΔH_sol (kJ mol⁻¹). Control: water volume, insulation, stirring, thermometer.

How does storage time affect the vitamin C content of blackcurrant squash, measured by titration against a standardised iodine solution?

Difficulty:

hard

Time:

multi-week

Equipment:

specialized

Analysis:

Beer-Lambert linearity

Feasibility:

2/5

Overused:

Less common

Biggest trap:

Concentration outside linear range

Variables · IV: days stored. DV: mg ascorbic acid per cm³. Control: dilution, starch indicator, storage temperature and light.

How does the concentration of hydrogen peroxide affect the rate of its catalysed decomposition, measured by O₂ volume against time?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

Uncertainty propagation

Feasibility:

3/5

Overused:

Less common

Biggest trap:

Electrolysis side reactions

Variables · IV: [H₂O₂]. DV: initial rate of O₂ evolution. Control: catalyst mass (MnO₂ or yeast), temperature, total volume.

How does adding a common ion (NaCl) affect the solubility of PbCl₂, determined by evaporating a saturated solution to constant mass?

Difficulty:

easy

Time:

1 week

Equipment:

school lab

Analysis:

t-test on gas volume

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

Pressure not equalised

Variables · IV: [NaCl] added. DV: dissolved PbCl₂ mass per 100 cm³. Control: temperature, equilibration time, filtration method.

Note · Lead salts are toxic — use small quantities, gloves, and the school's heavy-metal waste route.

How does the alcohol content stated on wine or beer compare to the value found by measuring the density of the distillate?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

Order from half-life

Feasibility:

4/5

Overused:

Less common

Biggest trap:

Clock reaction started late

Variables · IV: beverage sample. DV: % ABV from distillate density. Control: distillation volume collected, temperature of density measurement.

Note · Only if permitted by your school; the ethanol is distilled, not consumed.