How is the VCE Chemistry exam structured?

A single 2.5-hour paper plus 15 minutes reading time. 120 marks. Section A: 30 multiple choice (30 marks). Section B: short and extended response (90 marks). Covers Units 3 and 4 roughly equally with some integration questions.

What are the key topics in Unit 3?

Unit 3 covers: AoS 1 What are the options for energy production? (combustion, fuels, energy density, biofuels). AoS 2 How can the yield of a chemical product be optimised? (rate of reaction, equilibrium, Le Chatelier's principle, Kc, acids and bases, pH, Kw).

What are the key topics in Unit 4?

Unit 4 covers: AoS 1 How are organic compounds categorised, analysed and used? (functional groups, IUPAC nomenclature, organic reactions, biomolecules, biochemical fuels). AoS 2 What is the chemistry of food? (carbohydrates, proteins, lipids, vitamins, food analysis via chromatography and titration).

What are the most-tested calculation types?

Calorimetry ($Q = mc\Delta T$, then dividing by moles), equilibrium constant calculations (Kc and ICE tables), pH calculations (strong acids, weak acids with Ka, buffer pH), titration calculations (volume and concentration), percentage yield, and molar mass.

How are the multiple choice questions structured?

30 questions in Section A, 1 mark each. Mix of knowledge, application, and short calculations. Cover all four AoS. Calculator-active throughout (except Paper 1 of Methods, not applicable here). Time pressure: about 60 seconds per question.

What is the role of the data booklet?

VCAA provides a data booklet with periodic table, formulas, equations, and tabulated data (Ka, Kc, electrochemical series). Available in the exam. Familiarise yourself with the layout before the exam; some questions require looking up values.

VICChemistry

VCE Chemistry Unit 3+4 practice questions: the 2026 guide

A complete guide to VCE Chemistry Unit 3+4 practice questions and exam preparation. Exam structure, question types, marking criteria, sample questions by Area of Study, and the practice routine that secures top marks.

Generated by Claude Opus 4.816 min readVCAA-CHEM-PRACTICEUpdated 2026-06-21

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this guide is for
Exam structure
Question types
Marking criteria
Sample questions by Area of Study
Practice routine
Check your knowledge

What this guide is for

VCE Chemistry Unit 3-4 is examined through SACs and one end-of-year exam. The exam is the major component (50-60 percent of the study score). This guide covers exam structure, question types, marking criteria, and a six-week preparation routine.

Exam structure

Duration: 2 hours 30 minutes plus 15 minutes reading time.
Total marks: 120.
Section A: 30 multiple-choice questions, 1 mark each. 30 marks.
Section B: Short and extended response. 90 marks.

The exam covers all four areas of study.

Question types

Multiple choice (Section A): Knowledge recall, simple calculations, structure identification.
Short answer (Section B): 2-5 mark items. Specific calculations or short explanations.
Extended response (Section B): 5-10 mark items. Multi-step calculations, longer explanations, sometimes incorporating data analysis.

Marking criteria

VCAA rewards:

Correct calculations with appropriate working.
Significant figures consistent with the data (typically 3 sig fig).
Units (always include).
Chemical correctness (equations balanced, formulas correct).
Communication (clear scientific writing in explanations).

Top band requires excellence in all five.

Sample questions by Area of Study

Unit 3 AoS 1 (Energy)

Sample. Calculate the energy released when 5.0 g of methane is combusted completely. $\Delta H_c$ of methane = -890 kJ/mol.

Solution. Moles methane = 5.0 g / 16.04 g/mol = 0.312 mol. Energy = 0.312 × 890 = 278 kJ.

Reference reaction profile for the exothermic combustion of methane:

\Delta H = -890

kJ mol

^{-1}

sits between reactant and product plateaus, with

E_a

marking the activation energy.

Unit 3 AoS 2 (Equilibrium and acids)

Sample. A reaction A + B ⇌ C + D has $K_c = 4.0$ at a given temperature. At equilibrium, [A] = 0.20, [B] = 0.10, [C] = ?. [D] = 0.40.

Solution. $K_c = [C][D] / [A][B]$ . $4.0 = [C](0.40) / (0.20)(0.10) = 20[C]$ . $[C] = 0.20$ M.

Reference weak-acid plus strong-base curve for Unit 3 AoS 2 buffer and titration questions: read

pK_a

directly off the y-axis at half-equivalence.

Unit 4 AoS 1 (Organic)

Sample. Identify the IUPAC name of (CH3)2CHCH2CH(CH3)CH2OH.

Solution. Longest chain with -OH: 5 carbons starting from OH end. OH on C1 (after numbering to give OH lowest locant). Branches: methyl on C2 (or higher; check both directions). Final: 2,4-dimethylpentan-1-ol.

Unit 4 AoS 2 (Food chemistry)

Sample. Distinguish between saturated and unsaturated fats at the molecular level. State one health implication.

Solution. Saturated: triglycerides with no C=C double bonds in the fatty acid tails. Solid at room temperature. Found in animal fats. Unsaturated: triglycerides with one (mono-) or more (poly-) C=C in the fatty acid tails. Liquid at room temperature. Found in plant oils. Health: saturated fats associated with increased LDL cholesterol; unsaturated fats associated with health benefits.

Practice routine

Weeks 1-2 of revision: Key knowledge review. Use VCAA Study Design as checklist.
Weeks 3-4: Calculation drills. Calorimetry, Kc, pH, titrations, percentage yield.
Week 5: Past papers under timed conditions. Mark against assessor's reports.
Week 6: Weak-area focus. Identify specific knowledge gaps; drill those.

Check your knowledge

A broad VCAA-style set spanning Units 3 and 4 (equilibrium, electrochemistry, calorimetry, organic, analytical, food chemistry). Attempt under exam conditions, then check against the solutions block.

State Le Chatelier's principle and use it to predict the effect of increasing pressure on the equilibrium $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$ . (3 marks)
A galvanic cell is built from a $Zn/Zn^{2+}$ half-cell and a $Ag/Ag^+$ half-cell at standard concentrations and 25 degrees C. ( $E^\circ(Zn^{2+}/Zn) = -0.76 \ \text{V}$ , $E^\circ(Ag^+/Ag) = +0.80 \ \text{V}$ .) (a) Identify the anode, the cathode, and write the overall cell equation. (b) Calculate $E^\circ_{cell}$ . (c) Calculate the change in mass of the silver electrode after a current of 0.50 A flows for 30.0 minutes ( $A_r(Ag) = 107.9$ ). (6 marks)
For the equilibrium $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ , the initial concentrations in a 2.0 L sealed vessel are $[SO_2] = 0.40 \ \text{M}$ , $[O_2] = 0.20 \ \text{M}$ , $[SO_3] = 0 \ \text{M}$ . At equilibrium, $[SO_3] = 0.30 \ \text{M}$ . (a) Construct an ICE table. (b) Calculate $K_c$ at this temperature. (5 marks)
A 25.00 mL aliquot of a Murray-Darling water sample is titrated against $0.0500 \ \text{M HCl}$ to determine total carbonate alkalinity (assume all alkalinity is as $HCO_3^-$ ). The endpoint is reached at 14.30 mL. (a) Write the equation for the titration reaction. (b) Calculate the concentration of $HCO_3^-$ in mol L $^{-1}$ and in mg L $^{-1}$ ( $M(HCO_3^-) = 61.02$ ). (c) Compare the result with the Australian drinking-water guideline of 500 mg L $^{-1}$ for total dissolved solids and comment on suitability for irrigation. (5 marks)
The combustion of methane is exothermic, $\Delta H = -890 \ \text{kJ mol}^{-1}$ . (a) Calculate the volume of methane (at SLC, $V_m = 24.79 \ \text{L mol}^{-1}$ ) needed to heat 2.50 L of water from 18.0 degrees C to 95.0 degrees C, assuming 65 percent heat-transfer efficiency and $c_{water} = 4.18 \ \text{J g}^{-1} \text{K}^{-1}$ . (b) Comment on whether the assumption of complete combustion is realistic in a gas hot-water system. (5 marks)
An unknown organic compound $X$ has the empirical formula $C_3H_6O$ and $M = 58 \ \text{g mol}^{-1}$ . (a, 2) Determine the molecular formula. (b, 4) The $^1H$ NMR of $X$ shows a single peak. Its IR shows a strong absorption at $1715 \ \text{cm}^{-1}$ and no broad O-H. Identify $X$ and justify your reasoning. (c, 2) Predict the mass spectrum base peak and account for it. (8 marks)
A buffer solution is prepared by dissolving 0.20 mol of ethanoic acid and 0.10 mol of sodium ethanoate in water and diluting to 1.00 L. $pK_a$ of ethanoic acid $= 4.74$ . (a) Calculate the pH. (b) Calculate the pH after adding 0.020 mol of $NaOH$ (assume no volume change). (c) Explain why the pH change is small. (6 marks)
(a, 2) Define saturated and unsaturated fatty acids at the molecular level. (b, 3) Olive oil is roughly 75 percent oleic acid ( $C_{18}H_{34}O_2$ , one C=C). Calculate the mass of bromine ( $Br_2$ , $M = 159.8$ ) that would react completely with 5.00 g of oleic acid via addition across the double bond. (c, 2) Comment on why olive oil's iodine value is a useful measure for assessing oil oxidative stability. (7 marks)

Solutions

Q1: Le Chatelier's principle: if a system at dynamic equilibrium is disturbed, the system shifts in the direction that minimises the disturbance. For the Haber equilibrium, increasing pressure favours the side with fewer moles of gas. There are $1 + 3 = 4$ moles of gas on the reactant side and $2$ moles on the product side, so the equilibrium shifts to the right (toward $NH_3$ ), increasing the yield of ammonia.
Q2: (a) Zn is more readily oxidised (more negative $E^\circ$ ), so Zn is the anode: $Zn(s) \rightarrow Zn^{2+}(aq) + 2e^-$ . Ag is the cathode: $Ag^+(aq) + e^- \rightarrow Ag(s)$ . Overall: $Zn(s) + 2Ag^+(aq) \rightarrow Zn^{2+}(aq) + 2Ag(s)$ . (b) $E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = 0.80 - (-0.76) = +1.56 \ \text{V}$ . (c) Charge $Q = It = 0.50 \times 30.0 \times 60 = 900 \ \text{C}$ . Moles of $e^- = 900 / 96\,500 = 9.33 \times 10^{-3}$ . Moles of Ag deposited $= 9.33 \times 10^{-3}$ (1:1 ratio). Mass gained $= 9.33 \times 10^{-3} \times 107.9 = 1.01 \ \text{g}$ . The silver electrode gains 1.01 g.
Q3: (a) ICE table (concentrations in mol L $^{-1}$ ):

Species	$SO_2$	$O_2$	$SO_3$
Initial	0.40	0.20	0
Change	$-0.30$	$-0.15$	$+0.30$
Equilibrium	0.10	0.05	0.30

(b) $K_c = \dfrac{[SO_3]^2}{[SO_2]^2[O_2]} = \dfrac{(0.30)^2}{(0.10)^2 (0.05)} = \dfrac{0.090}{5.0 \times 10^{-4}} = 1.8 \times 10^{2} \ \text{M}^{-1}$ . The equilibrium constant at this temperature is $1.8 \times 10^{2} \ \text{M}^{-1}$ , indicating products are strongly favoured.

Q4: (a) $HCO_3^- + H^+ \rightarrow H_2CO_3 \rightarrow H_2O + CO_2$ . Net: $HCO_3^- + HCl \rightarrow Cl^- + H_2O + CO_2$ . (b) $n(HCl) = 0.0500 \times 0.01430 = 7.15 \times 10^{-4} \ \text{mol}$ . $n(HCO_3^-) = 7.15 \times 10^{-4}$ (1:1). $[HCO_3^-] = 7.15 \times 10^{-4} / 0.02500 = 2.86 \times 10^{-2} \ \text{mol L}^{-1}$ . Mass concentration $= 2.86 \times 10^{-2} \times 61.02 = 1.75 \ \text{g L}^{-1} = 1750 \ \text{mg L}^{-1}$ . (c) Well above the 500 mg L $^{-1}$ TDS guideline for drinking water. For irrigation the high bicarbonate alkalinity can raise soil pH and cause sodium-bicarbonate interaction with clay particles; the water would need to be diluted with rainwater or remediated before sustained crop use.
Q5: (a) Energy needed to heat water: $Q = mc\Delta T = 2500 \times 4.18 \times (95.0 - 18.0) = 8.047 \times 10^{5} \ \text{J} = 804.7 \ \text{kJ}$ . At 65 percent efficiency, fuel energy required $= 804.7 / 0.65 = 1238 \ \text{kJ}$ . Moles methane $= 1238 / 890 = 1.391 \ \text{mol}$ . Volume at SLC $= 1.391 \times 24.79 = 34.5 \ \text{L}$ . (b) In a well-tuned domestic gas heater combustion is close to complete, but the air-to-gas ratio fluctuates and some CO is produced. The complete-combustion assumption typically overstates the heat output by a few percent.
Q6: (a) Empirical mass $= 3(12.01) + 6(1.01) + 16.00 = 58.08 \ \text{g mol}^{-1}$ , matching $M$ . The molecular formula equals the empirical formula: $C_3H_6O$ . (b) A single $^1H$ NMR peak means all the H environments are equivalent. The IR carbonyl absorption at $1715 \ \text{cm}^{-1}$ is in the ketone/aldehyde region; absence of broad O-H rules out a carboxylic acid. Six equivalent H and a C=O fits propan-2-one (acetone, $CH_3COCH_3$ ): two equivalent methyl groups on a central carbonyl. (c) Cleavage of one methyl-acyl bond gives the acylium cation $[CH_3CO]^+$ at $m/z = 43$ , the well-known base peak of acetone (with the parent ion at $m/z = 58$ ).
Q7: (a) Using Henderson-Hasselbalch: $pH = pK_a + \log_{10}\dfrac{[A^-]}{[HA]} = 4.74 + \log_{10}\dfrac{0.10}{0.20} = 4.74 - 0.301 = 4.44$ . (b) Adding $0.020 \ \text{mol}$ NaOH converts $0.020 \ \text{mol}$ acid to acetate: new moles acid $= 0.18$ , acetate $= 0.12$ . $pH = 4.74 + \log_{10}(0.12/0.18) = 4.74 - 0.176 = 4.56$ . (c) The added strong base is consumed by the weak acid, generating more conjugate base; the ratio $[A^-]/[HA]$ changes only modestly, so $pH$ shifts by only 0.12 units. This is the defining behaviour of an effective buffer (operating within $\pm 1$ unit of $pK_a$ ).
Q8: (a) Saturated fatty acids contain only single C-C bonds in the hydrocarbon tail; unsaturated fatty acids contain one or more C=C double bonds (mono- or poly-unsaturated). (b) Moles of oleic acid $= 5.00 / 282.5 = 1.770 \times 10^{-2} \ \text{mol}$ (using $M(C_{18}H_{34}O_2) = 282.5$ ). One $Br_2$ adds per C=C, so moles $Br_2 = 1.770 \times 10^{-2}$ . Mass $Br_2 = 1.770 \times 10^{-2} \times 159.8 = 2.83 \ \text{g}$ . (c) The iodine (or bromine) value measures the degree of unsaturation in a fat or oil. Polyunsaturated oils with high iodine values are more prone to free-radical oxidation at the C=C sites (rancidity), so iodine value is a direct proxy for oxidative stability and shelf life.