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AP®ChemistryCollege BoardExam QuestionsUnit 2: Compound Structure & PropertiesIonic Crystals & Metals

Ionic Crystals & Metals (College Board AP® Chemistry): Exam Questions

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Ionic Crystals & Metals

Medium
Hard
1a2 marks

Compound

Melting Point (°C)

LiI

449

KI

686

LiF

845

NaF

993

A student learns that ionic compounds have significant covalent character when a cation has a polarizing effect on a large anion. As a result, the student hypothesizes that salts composed of small cations and large anions should have relatively low melting points.

Select two compounds from the table and explain how the data support the student’s hypothesis.

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1b2 marks

Identify a compound from the table that can be dissolved in water to produce a basic solution. Write the net ionic equation for the reaction that occurs to cause the solution to be basic.

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2a2 marks

Cation

Ionic Radius (pm)

Charge

Na+

102

+1

Mg2+

72

+2

Al3+

53

+3

Explain, using Coulomb’s Law, why MgCl2 has a higher lattice energy than NaCl.

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2b2 marks

Predict whether AlCl3 has a higher or lower lattice energy than MgCl2, and justify your prediction.

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3a2 marks

A manufacturer is designing a high-stress bridge component and must choose between steel (Fe-C alloy) and brass (Cu-Zn alloy).

Explain the structural difference between interstitial and substitutional alloys.

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3b2 marks

Predict whether steel or brass will be harder, and justify your answer in terms of atomic structure and metallic bonding.

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4a1 mark

A researcher is studying the properties of silver (Ag), nickel (Ni), and silver bromide (AgBr), which differ in bonding type and electrical behavior. These substances are used in photography, electronics, and electrochemical processes.

Identify the type of solid formed by AgBr and justify your answer in terms of the particles and forces involved.

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4b1 mark

Predict whether AgBr or NaBr has a higher lattice energy. Justify your answer.

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4c1 mark

AgBr is used in photographic film because it undergoes decomposition when exposed to light.

Write a balanced equation for the photochemical decomposition of AgBr.

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4d1 mark

Explain why metallic silver conducts electricity, but solid AgBr does not.

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4e1 mark

A nickel solution is often used in electroplating.

Write the half-equation for the reduction of Ni²⁺ to Ni(s), and
identify what type of bonding is present in the plated nickel layer.

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4f1 mark

Predict which substance, Ag or AgBr, is more malleable and justify your answer based on the bonding and structure of the solid.

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4g2 marks

Silver bromide (AgBr) is a sparingly soluble salt. The Ksp of AgBr is 5.0 × 10⁻¹³ at 25 °C.

Calculate the molar solubility of AgBr in pure water at this temperature. Show all working.

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4h2 marks

A solution is prepared by mixing AgNO3 and NaBr, each at an initial concentration of 1.00 × 10-4 M.

Predict whether a precipitate of AgBr will form.
Justify your answer by calculating the ion product Q and comparing it to Ksp.

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1a1 mark

A student is investigating the properties of two solid samples: magnesium fluoride (MgF2) and tungsten (W).

Explain how the structure of MgF2 contributes to its high melting point using Coulomb’s Law.

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1b2 marks

Magnesium fluoride and tungsten have different electrical conductivity properties in the solid state.

Explain these differences in terms of their bonding and particle arrangement.

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1c1 mark

A researcher applies an external force to both MgF2 and W. Predict which material is more likely to fracture and justify your answer in terms of bonding and atomic interactions.

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2a2 marks

A manufacturer is developing a high-temperature, high-stress aerospace component and is considering two alloys:

  • Steel (an interstitial alloy of iron and carbon)

  • Brass (a substitutional alloy of copper and zinc)

The engineers are concerned about hardness, resistance to deformation, and performance under repeated mechanical stress cycles at extreme temperatures.

Explain how the atomic structure of steel and brass leads to differences in their mechanical strength and resistance to deformation.

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2b2 marks

At high temperatures, one of these alloys will undergo greater structural weakening due to atomic diffusion.

Predict which alloy is more likely to weaken. Justify your answer based on atomic structure and bonding principles.

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3a2 marks

A scientist is studying the behavior of two solid materials when subjected to high temperatures and electrical currents:

  • Aluminum (Al) – a metallic solid commonly used in electrical wiring.

  • Calcium fluoride (CaF2) – an ionic solid used in optical coatings and furnace linings.

Explain why aluminum is an electrical conductor in the solid state, whereas solid calcium fluoride is not.

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3b2 marks

When both solids are heated, one expands more significantly than the other. Predict which material will expand more and justify your answer in terms of atomic interactions and bonding forces.

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