AP Chemistry Practice Exam: Full-Length Multiple Choice

Topic 1.1 · Apply it

How many water molecules are in 9.0 g of water (molar mass 18.0 g/mol)?

Topic 1.2 · Data analysis

Which element is this most likely to be?

Topic 1.4 · Apply it

A 10.0 g mixture of sodium chloride (NaCl, 58.44 g/mol) and sand contains 2.00 g of chlorine. The sand contains no chlorine. What mass of NaCl is in the mixture?

Topic 1.5 · Apply it

According to Coulomb's law, which change increases the attraction between a nucleus and an electron the most?

Topic 1.7 · Apply it

The first ionization energy of oxygen is slightly lower than that of nitrogen, even though oxygen has more protons. Which explanation is best?

Topic 1.8 · Apply it

Magnesium and chlorine form an ionic compound. What is its formula?

Topic 2.1 · Apply it

A white solid doesn't conduct electricity, but it does when melted or dissolved in water. It has a very high melting point. What kind of bonding does it most likely have?

Topic 2.2 · Data analysis

On a graph of potential energy against the distance between two hydrogen nuclei, what does the distance at the lowest point of the curve represent?

Topic 2.4 · Apply it

Steel is iron with a small amount of carbon. Why is it harder than pure iron?

Topic 2.5 · Apply it

In the Lewis diagram of ammonia, NH₃, how many lone pairs are on the nitrogen atom?

Topic 2.6 · Apply it

Formal charge helps choose between possible Lewis structures. For carbon dioxide, which structure is preferred?

Topic 2.7 · Apply it

Why is the H–O–H bond angle in water (about 104.5°) smaller than the H–C–H angle in methane (109.5°)?

Topic 3.1 · Apply it

Hydrogen fluoride (HF) boils at 20 °C, while hydrogen chloride (HCl) boils at −85 °C. What best explains the difference?

Topic 3.2 · Apply it

Silicon dioxide (SiO₂, quartz) melts above 1,600 °C, while carbon dioxide is a gas at room temperature. Why?

Topic 3.3 · Concept check

Compared with the same substance as a gas, the particles in a liquid are:

Topic 3.4 · Apply it

A gas sample occupies 12.3 L at 2.00 atm and 27 °C. How many moles of gas are present? (R = 0.08206 L·atm·mol⁻¹·K⁻¹)

Topic 3.5 · Apply it

Helium and argon are in separate containers at the same temperature. Which statement is correct?

Topic 3.6 · Concept check

Under which conditions does a real gas deviate most from ideal behaviour?

Topic 3.7 · Apply it

5.85 g of NaCl (58.44 g/mol) is dissolved in water to make 250. mL of solution. What is the molarity?

Topic 3.8 · Apply it

Which description best represents how water molecules surround the ions in an NaCl solution?

Topic 3.9 · Experiment

A student wants to separate a mixture of two miscible liquids with boiling points of 78 °C and 100 °C. Which method is most appropriate, and why does it work?

Topic 3.10 · Apply it

Iodine (I₂) dissolves much better in hexane (C₆H₁₄) than in water. Which explanation is best?

Topic 3.11 · Concept check

Which molecular change is caused mainly by absorbing infrared radiation?

Topic 3.12 · Apply it

What is the energy of one photon of light with a wavelength of 500. nm? (h = 6.626 × 10⁻³⁴ J·s, c = 3.00 × 10⁸ m/s)

Topic 3.13 · Data analysis

Using Beer's law, what is the concentration of the unknown?

Topic 4.1 · Apply it

Which observation is the best evidence that a chemical reaction has occurred when two clear solutions are mixed?

Topic 4.3 · Apply it

Propane burns according to the equation C₃H₈ + __O₂ → 3CO₂ + 4H₂O. What coefficient balances O₂?

Topic 4.5 · Apply it

Hydrogen burns in oxygen: 2H₂ + O₂ → 2H₂O. What mass of water forms from 4.0 g of H₂ (2.0 g/mol) with excess oxygen? (H₂O = 18.0 g/mol)

Topic 4.6 · Experiment

In a titration, 25.0 mL of HCl is exactly neutralised by 20.0 mL of 0.100 M NaOH. What is the concentration of the HCl?

Topic 4.8 · Apply it

In the reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, what role does water play?

Topic 5.1 · Apply it

For 2NO₂(g) → 2NO(g) + O₂(g), NO₂ is consumed at 0.040 M/s. At what rate is O₂ produced?

Topic 5.2 · Data analysis

In experiments on A + B → C, doubling [B] while keeping [A] constant leaves the initial rate unchanged. What is the order with respect to B?

Topic 5.4 · Apply it

The step 2NO(g) + O₂(g) → 2NO₂(g) is an elementary reaction. What is its rate law?

Topic 5.6 · Data analysis

On an energy profile, the reactants are at 50 kJ, the transition state is at 120 kJ and the products are at 20 kJ.

What are the activation energy of the forward reaction and the enthalpy change?

Topic 5.9 · Apply it

Step 1 (fast, reaches equilibrium): 2NO ⇌ N₂O₂
Step 2 (slow): N₂O₂ + O₂ → 2NO₂

Using the pre-equilibrium approximation, which rate law matches this mechanism?

Topic 6.1 · Apply it

When ammonium nitrate dissolves in water in a cold pack, the pack gets cold. Which statement is correct?

Topic 6.2 · Data analysis

On an energy diagram, the products of a reaction are lower in energy than the reactants. What does this show?

Topic 6.4 · Apply it

How much heat is needed to raise the temperature of 100.0 g of water by 5.00 °C? (c = 4.18 J/(g·°C))

Topic 6.6 · Apply it

For 2H₂(g) + O₂(g) → 2H₂O(l), ΔH = −572 kJ. How much heat is released when 1.00 mol of H₂ burns?

Topic 6.7 · Apply it

Use bond enthalpies to estimate ΔH for H₂(g) + Cl₂(g) → 2HCl(g). (H–H 436 kJ/mol, Cl–Cl 243 kJ/mol, H–Cl 432 kJ/mol)

Topic 7.1 · Concept check

Which statement is true for a reaction at equilibrium?

Topic 7.3 · Concept check

What is the equilibrium constant expression for N₂(g) + 3H₂(g) ⇌ 2NH₃(g)?

Topic 7.5 · Apply it

A reaction has K = 1 × 10¹⁰ at 25 °C. What does this tell you about the equilibrium mixture?

Topic 7.7 · Apply it

For A(aq) ⇌ B(aq), K = 3.0. A solution starts with [A] = 0.40 M and no B. What are the equilibrium concentrations?

Topic 7.10 · Apply it

N₂(g) + 3H₂(g) ⇌ 2NH₃(g) is at equilibrium. The container volume is suddenly doubled at constant temperature. How does Q compare with K, and which way does the system shift?

Topic 8.1 · Apply it

At 25 °C, a solution has [H₃O⁺] = 1.0 × 10⁻³ M. What is [OH⁻]? (Kw = 1.0 × 10⁻¹⁴)

Topic 8.2 · Apply it

What is the pH of 0.010 M HCl?

Topic 8.2 · Apply it

What is the pH of 0.0010 M NaOH at 25 °C?

Topic 8.3 · Apply it

What is the pH of 0.10 M of a weak acid with Ka = 1.0 × 10⁻⁵?

Topic 8.5 · Data analysis

Acetic acid is titrated with NaOH. Why is the pH at the equivalence point greater than 7?

Topic 8.5 · Data analysis

In the titration of a weak acid with a strong base, the pH at the half-equivalence point is 4.74. What is the acid's pKa?

Topic 8.6 · Apply it

Perchloric acid (HClO₄) is a much stronger acid than hypochlorous acid (HClO). Which explanation is best?

Topic 8.8 · Apply it

A small amount of HCl is added to an acetic acid/acetate buffer. Why does the pH change only slightly?

Topic 8.9 · Apply it

A buffer contains a weak acid with pKa = 4.74, and [A⁻]/[HA] = 10. What is its pH?

Topic 8.10 · Apply it

Buffer X is 0.10 M acetic acid and 0.10 M sodium acetate. Buffer Y is 1.0 M of each. Which statement is correct?

Topic 9.1 · Apply it

Which process has a positive entropy change (ΔS > 0)?

Topic 9.3 · Apply it

A reaction has ΔH < 0 and ΔS < 0. When is it thermodynamically favourable?

Topic 9.5 · Concept check

A reaction has a negative ΔG° at 25 °C. What does this tell you about its equilibrium constant?

Topic 9.7 · Apply it

A reaction with ΔG° = +14 kJ/mol is coupled with ATP hydrolysis (ΔG° = −31 kJ/mol). What is ΔG° for the coupled process, and is it favourable?

Topic 9.9 · Apply it

For the zinc–copper cell, E°cell = +1.10 V and n = 2. What is ΔG°? (F = 96,485 C/mol)