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

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.

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.

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.

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

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.

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

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

Write a balanced equation for the photochemical decomposition of AgBr.

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

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.

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

Silver bromide (AgBr) is a sparingly soluble salt. The K_sp 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.

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 K_sp.

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.

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

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

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.

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

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

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.

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.

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.

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.