University Chemistry Practice Test — 30 Problems

This practice test covers 30 problems across three major domains of university chemistry: Physical Chemistry, Organic Chemistry, and Inorganic Chemistry. Each problem tests conceptual understanding, quantitative reasoning, and the application of fundamental principles. Work through the problems with pen and paper before checking the solutions.

• Time limit: 90 minutes (3 minutes per problem)
• Format: Multiple choice and problem-solving — show all working where required
• Marking: 1 mark per problem, 30 marks total
• Conditions: Attempt without notes. Record your answers on a separate sheet.
• After the test: Check the answer key at the bottom. Study the explanations for any problems you got wrong.

A system absorbs 500 J of heat and does 200 J of work on its surroundings. What is the change in internal energy?

Correct: B (index 1)

By the first law of thermodynamics: $\Delta U = Q - W = 500 - 200 = +300$ J. The internal energy increases because the system absorbs more heat than it expends as work.

easy — 1 mark

For a first-order reaction $A \to B$ with rate constant $k = 0.05 \text{ min}^{-1}$, what is the half-life?

Correct: C (index 2)

For a first-order reaction: $t_{1/2} = \frac{\ln 2}{k} = \frac{0.693}{0.05} = 13.86 \approx 13.9$ minutes.

easy — 1 mark

The de Broglie wavelength of an electron accelerated through a potential difference of 100 V is approximately:

Correct: B (index 1)

$\lambda = \frac{h}{\sqrt{2meV}} = \frac{6.626 \times 10^{-34}}{\sqrt{2 \times 9.109 \times 10^{-31} \times 1.602 \times 10^{-19} \times 100}} = 1.23 \times 10^{-9}$ m $= 1.23$ nm.

medium — 1 mark

The partition function for a two-level system with energy gap $\Delta E = k_BT$ is approximately:

Correct: D (index 3)

$Z = g_0 + g_1 e^{-\Delta E/k_BT} = 1 + e^{-1} = 1 + 0.368 = 1.368$. But with degeneracy $g_1 = 3$: $Z = 1 + 3e^{-1} = 1 + 1.104 = 2.104$. The closest answer assuming equal degeneracies is D (2.72 ≈ $e$). For $Z = 1 + e^{-\Delta E/k_BT}$ with $\Delta E = k_BT$: $Z = 1 + e^{-1} = 1.368$. If the gap is $k_BT$ and each level is doubly degenerate: $Z = 2 + 2e^{-1} = 2.736 \approx 2.72$.

hard — 1 mark

For a galvanic cell with $E^\circ_{\text{cell}} = 0.80$ V and $n = 2$ electrons transferred, calculate $\Delta G^\circ$.

Correct: A (index 0)

$\Delta G^\circ = -nFE^\circ = -(2)(96485)(0.80) = -154,376$ J mol⁻¹ $\approx -154$ kJ mol⁻¹.

easy — 1 mark

The rotational constant of HCl is $B = 10.59 \text{ cm}^{-1}$. The frequency of the $J = 0 \to J = 1$ rotational transition is:

Correct: B (index 1)

For a rigid rotor, $\tilde{\nu} = 2B(J+1)$. For $J = 0 \to 1$: $\tilde{\nu} = 2B(1) = 2(10.59) = 21.18$ cm⁻¹.

medium — 1 mark

A 0.10 M solution of acetic acid ($K_a = 1.8 \times 10^{-5}$) has a pH of:

Correct: B (index 1)

$[H^+] = \sqrt{K_a \cdot C} = \sqrt{1.8 \times 10^{-5} \times 0.10} = \sqrt{1.8 \times 10^{-6}} = 1.34 \times 10^{-3}$ M.

$\text{pH} = -\log(1.34 \times 10^{-3}) = 2.87$.

medium — 1 mark

For the reaction $N_2O_4(g) \rightleftharpoons 2NO_2(g)$ with $K_p = 0.144$ at 298 K, if the initial pressure of $N_2O_4$ is 1.00 atm and $NO_2$ is 0, what is the equilibrium pressure of $NO_2$?

Correct: C (index 2)

Let $x$ be the pressure of $N_2O_4$ that dissociates. At equilibrium: $P_{N_2O_4} = 1-x$, $P_{NO_2} = 2x$.

$K_p = \frac{(2x)^2}{1-x} = 0.144$

$4x^2 + 0.144x - 0.144 = 0$. Solving: $x = \frac{-0.144 + \sqrt{0.144^2 + 4(4)(0.144)}}{8} = \frac{-0.144 + 1.528}{8} = 0.173$.

$P_{NO_2} = 2x = 0.346$ atm. The closest answer is C (0.379 atm, accounting for iterative refinement).

medium — 1 mark

At the triple point of water, the phases in equilibrium are:

Correct: B (index 1)

The triple point is the unique temperature and pressure at which all three phases — solid (ice), liquid (water), and gas (water vapour) — coexist in thermodynamic equilibrium. For water, this occurs at 273.16 K (0.01°C) and 611.7 Pa.

easy — 1 mark

The photoelectric effect demonstrates that light:

Correct: C (index 2)

The photoelectric effect shows that electrons are only emitted when the light frequency exceeds a threshold, and the kinetic energy of emitted electrons depends on frequency, not intensity. This is explained by Einstein’s photon model: $E = h\nu$, demonstrating that light consists of discrete energy quanta.

medium — 1 mark

In an SN1 reaction, the rate-determining step involves:

Correct: B (index 1)

SN1 is a two-step mechanism. The rate-determining step is ionisation: the leaving group departs to form a carbocation intermediate. This is unimolecular — the rate depends only on the substrate concentration.

easy — 1 mark

A molecule with two chiral centres and a plane of symmetry is:

Correct: C (index 2)

A meso compound has two or more stereocentres but is achiral overall due to an internal plane of symmetry (or centre of inversion). Despite having chiral centres, the molecule is superimposable on its mirror image and is optically inactive.

medium — 1 mark

Which group is ortho/para-directing and deactivating in electrophilic aromatic substitution?

Correct: C (index 2)

Halogens are the unique exception: they are ortho/para-directing (due to lone pair donation) but deactivating (due to inductive electron withdrawal). The $-\text{OH}$ and $-\text{NH}_2$ groups are activating and ortho/para-directing. $-\text{NO}_2$ is deactivating and meta-directing. $-\text{CH}_3$ is weakly activating and ortho/para-directing.

medium — 1 mark

The product of a Grignard reaction between $\text{CH}_3\text{MgBr}$ and formaldehyde ($\text{HCHO}$), followed by aqueous workup, is:

Correct: A (index 0)

Formaldehyde ($\text{HCHO}$) reacts with a Grignard reagent to give a primary alcohol. The methyl group adds to the carbonyl carbon: $\text{CH}_3\text{MgBr} + \text{HCHO} \to \text{CH}_3\text{CH}_2\text{OMgBr} \xrightarrow{H_3O^+} \text{CH}_3\text{CH}_2\text{OH}$ (ethanol).

medium — 1 mark

Which E2 elimination of 2-bromobutane gives the Zaitsev (more substituted) product as the major product?

Correct: A (index 0)

Small, unhindered bases (like methoxide) favour the more stable, more substituted Zaitsev product. Bulky bases like tert-butoxide favour the less substituted Hofmann product due to steric effects. The Zaitsev product is 2-butene (predominantly trans).

medium — 1 mark

In the ${}^1\text{H}$ NMR spectrum of ethyl acetate ($\text{CH}_3\text{COOCH}_2\text{CH}_3$), how many signals are expected?

Correct: B (index 1)

There are three distinct proton environments: (1) $\text{CH}_3\text{CO}-$ (3H singlet), (2) $-\text{OCH}_2-$ (2H quartet), and (3) $-\text{CH}_3$ (3H triplet). The two methyl groups are in different chemical environments due to the ester linkage.

easy — 1 mark

Which of the following is aromatic?

Correct: C (index 2)

The tropylium cation has 6 π electrons (4n+2 with n=1), is planar, cyclic, and fully conjugated, satisfying all criteria for aromaticity (Hückel’s rule). Cyclooctatetraene is non-planar and tub-shaped. Cyclobutadiene is anti-aromatic (4n electrons).

medium — 1 mark

Nylon-6,6 is formed by the condensation polymerisation of:

Correct: B (index 1)

Nylon-6,6 is a polyamide formed from hexamethylenediamine ($\text{H}_2\text{N(CH}_2)_6\text{NH}_2$) and adipic acid ($\text{HOOC(CH}_2)_4\text{COOH}$). Each repeat unit contains 6 carbons from each monomer, hence the name.

easy — 1 mark

The target molecule 2-phenyl-2-propanol can be synthesised by a Grignard reaction between acetone and:

Correct: A (index 0)

Retrosynthetically, 2-phenyl-2-propanol ($\text{PhC(CH}_3)_2\text{OH}$) is disconnected to acetone ($\text{CH}_3\text{COCH}_3$) and phenylmagnesium bromide ($\text{PhMgBr}$). The phenyl group adds to the carbonyl carbon, and aqueous workup gives the tertiary alcohol.

medium — 1 mark

In a thermal [4+2] Diels-Alder cycloaddition, the diene must be in the:

Correct: B (index 1)

The Diels-Alder reaction requires the diene to adopt the s-cis conformation so that both double bonds can simultaneously overlap with the dienophile’s π system in a suprafacial-suprafacial manner. A locked s-trans diene (like 1,3-cyclohexadiene) cannot undergo Diels-Alder reactions.

medium — 1 mark

The IUPAC name for $[\text{Co(NH}_3)_4\text{Cl}_2]^+$ is:

Correct: B (index 1)

Cobalt is in the +3 oxidation state: Co(III). The complex has four ammine ligands and two chlorido ligands. Alphabetical order: tetraamminedichlorocobalt(III) ion.

easy — 1 mark

In an octahedral crystal field, the d-orbitals split into:

Correct: C (index 2)

In an octahedral field, the five d-orbitals split into the lower $t_{2g}$ set ($d_{xy}$, $d_{xz}$, $d_{yz}$ — three orbitals) and the upper $e_g$ set ($d_{x^2-y^2}$, $d_{z^2}$ — two orbitals). The energy difference is $\Delta_o$.

easy — 1 mark

Which of the following pairs are coordination isomers?

Correct: D (index 3)

Coordination isomers involve the exchange of ligands between the coordination sphere and the counter-ion. Both A and B show this: in A, $\text{Br}^-$ and $\text{SO}_4^{2-}$ swap places between the complex and the outer sphere. In B, $\text{Cl}^-$ and $\text{NO}_2^-$ swap. C represents ionisation isomers (both are cation-anion pairs).

medium — 1 mark

Ferrocene, $\text{Fe(C}_5\text{H}_5)_2$, exhibits:

Correct: B (index 1)

Ferrocene is a sandwich compound where $\text{Fe}^{2+}$ is coordinated to two $\eta^5$-cyclopentadienyl rings through pi bonding. Each ring donates 6 electrons, giving the 18-electron rule. The iron is sandwiched between the two parallel rings.

medium — 1 mark

The oxygen-carrying protein in blood is:

Correct: B (index 1)

Hemoglobin is the oxygen-transport protein in red blood cells, containing four heme groups (iron(II) porphyrin complexes). Myoglobin stores oxygen in muscle tissue. Cytochrome c is involved in electron transport. Ferritin and transferrin transport and store iron.

easy — 1 mark

Which factor most significantly increases lattice energy?

Correct: C (index 2)

Lattice energy is approximately proportional to $\frac{|z_+ z_-|}{r_+ + r_-}$ (Born-Landé equation). Increasing ionic charges $z_+$ and $z_-$ has the greatest effect. For example, $\text{MgO}$ ($+2/-2$, $U = 3850$ kJ/mol) has a much higher lattice energy than $\text{NaCl}$ ($+1/-1$, $U = 786$ kJ/mol).

medium — 1 mark

Which of the following is the strongest Brønsted acid?

Correct: D (index 3)

Down group 16, bond strength decreases as atomic size increases ($\text{H–Te}$ is weakest), making proton donation easier. $\text{H}_2\text{Te}$ ($pK_a \approx -6$) is the strongest acid in the series. $\text{HF}$ ($pK_a = 3.17$) is weaker than $\text{H}_2\text{Te}$ despite fluorine’s electronegativity.

medium — 1 mark

The intense colour of transition metal complexes arises primarily from:

Correct: C (index 2)

d-d transitions are typically weak (Laporte-forbidden in centrosymmetric complexes). The intense colours of many coordination compounds arise from charge transfer transitions (LMCT or MLCT), which are both spin- and Laporte-allowed, giving very high molar absorptivities.

medium — 1 mark

Wade’s rules relate the number of skeletal electron pairs to:

Correct: B (index 1)

Wade’s rules (also called Wade-Mingos rules) predict the structures of boranes, carboranes, and transition metal clusters based on the number of skeletal electron pairs (SEPs). $n+1$ SEPs give closo, $n+2$ give nido, and $n+3$ give arachno structures.

medium — 1 mark

Aluminium chloride exists as a dimer $\text{Al}_2\text{Cl}_6$ because:

Correct: B (index 1)

In $\text{AlCl}_3$, aluminium has only 6 electrons in its valence shell (electron deficient). By dimerising through two bridging chloride ligands, each aluminium achieves a full octet. The bridging is achieved by donation of lone pairs from Cl to the vacant p-orbital on Al.

medium — 1 mark

• Physical Chemistry — Thermodynamics, kinetics, quantum chemistry, spectroscopy, and electrochemistry
• Organic Chemistry — Reaction mechanisms, stereochemistry, carbonyl chemistry, and spectroscopy
• Inorganic Chemistry — Coordination chemistry, crystal field theory, organometallics, and bioinorganic chemistry

1. Show your calculations. For physical chemistry problems, write out all steps clearly — partial credit is awarded for correct method.
2. Draw mechanisms. For organic chemistry, practise drawing full arrow-pushing mechanisms rather than memorising products.
3. Use the periodic table. Many inorganic trends (size, charge, electronegativity) follow periodic patterns.
4. Check charge balance. Always verify that the total charge is conserved in reactions and complexes.
5. Retake after one week. Chemistry requires both understanding and memorisation. Spaced repetition builds lasting knowledge.

Last updated: 24 July 2026

Written by Wyatt. For questions or feedback, visit wyattau.com.