Which crystal system has a = b ≠ c and α = β = γ = 90°?
Correct answer B. Tetragonal
Topic / 40 questions
Solids MCQs
Solids MCQs are multiple-choice questions on crystalline and amorphous solids, crystal lattices, unit cells, the types of crystals and lattice energy. They follow the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly, which makes it easy to revise definitions and properties in short sessions.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
Two different substances that have the same crystal structure are called ____
Correct answer B. isomorphic
Polymorphism shown by an element, such as diamond and graphite for carbon, is called ____
Correct answer A. allotropy
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The temperature at which two crystalline forms of a substance can exist together in equilibrium is called the ____
Correct answer D. transition temperature
How many parameters are needed to describe a unit cell completely?
Correct answer B. Six
How many Bravais lattices are possible in three dimensions?
Correct answer D. 14
An ionic crystal has a cation to anion radius ratio between 0.225 and 0.414. What arrangement is expected around each cation?
Correct answer A. Tetrahedral, coordination number 4
Diamond is an example of which type of crystalline solid?
Correct answer A. Covalent (network) crystal
Why do metallic crystals conduct electricity in the solid state?
Correct answer A. They contain mobile valence electrons
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Ice is a molecular crystal in which the molecules are held together mainly by ____
Correct answer C. hydrogen bonds
Using lattice energy (KCl) = −718, ΔHsub(K) = +89, IE(K) = +419, ½BDE(Cl₂) = +122 and EA(Cl) = −349 kJ mol⁻¹, what is ΔHf of KCl?
Correct answer A. −437 kJ mol⁻¹
Which order of lattice energy (magnitude) is correct for the alkali metal fluorides?
Correct answer D. LiF > NaF > KF
How many atoms belong to one body-centred cubic (bcc) unit cell?
Correct answer A. 2
What is the coordination number of each atom in a cubic close-packed (face-centred cubic) metal crystal?
Correct answer C. 12
In the sodium chloride crystal, the six Cl⁻ ions surrounding each Na⁺ ion lie at the corners of a ____
Correct answer D. regular octahedron
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When a crystalline solid is cut with a sharp edge, it splits along definite smooth surfaces. These are called ____
Correct answer D. cleavage planes
Why are amorphous solids sometimes described as supercooled liquids?
Correct answer A. Their particles lack long-range order, like those of a liquid
What is the coordination number of each ion in the caesium chloride crystal?
Correct answer B. 8
Using ΔHf(NaCl) = −411, ΔHsub(Na) = +108, IE(Na) = +496, ½BDE(Cl₂) = +121 and EA(Cl) = −349 kJ mol⁻¹, what is the lattice energy of NaCl?
Correct answer B. −787 kJ mol⁻¹
Why does solid iodine sublime easily on gentle heating while sodium chloride does not?
Correct answer A. I₂ molecules are held by weak London forces, whereas NaCl has strong ionic bonds
About Solids MCQs
This topic starts with the differences between crystalline and amorphous solids, including sharp melting points, anisotropy and long-range order. Questions then move to the crystal lattice, the unit cell and the seven crystal systems with their unit cell parameters, such as a = b = c and α = β = γ = 90° for the cubic system. The second part compares ionic, molecular, covalent and metallic crystals by their bonding, hardness, melting point and conductivity. You will also be asked about the factors that decide the shape of ionic crystals, such as the radius ratio of the ions, and about lattice energy: what it means, how ionic charge and size affect it and how it is found.
Key facts to remember
- Crystalline solids have a regular three-dimensional arrangement of particles and sharp melting points; amorphous solids lack long-range order and soften over a range of temperatures.
- A unit cell is the smallest repeating unit that generates the whole crystal lattice when repeated in three dimensions.
- Crystals are classified into seven crystal systems; in the cubic system a = b = c and α = β = γ = 90°.
- Lattice energy is the energy released when one mole of an ionic crystal is formed from its gaseous ions.
- Lattice energy is larger for ions with higher charges and smaller radii.
- Molecular crystals such as ice, iodine and dry ice are held by weak intermolecular forces, so they are soft, have low melting points and do not conduct electricity.
Exams that include Solids MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Solids MCQs
- Make a comparison table of ionic, molecular, covalent and metallic crystals with examples and properties.
- Learn the unit cell parameters of at least the cubic, tetragonal and hexagonal systems.
- Remember that lattice energy depends on charge and size, and compare compounds such as NaCl and MgO on that basis.
- Revise lattice energy together with the Born–Haber cycle in Thermochemistry, since the two are often combined.
Frequently asked questions
What does the MDCAT syllabus include in Solids?
The PMDC MDCAT curriculum for Solids covers crystalline solids, the factors affecting the shape of ionic crystals, the comparison of ionic and molecular crystals, the crystal lattice and lattice energy.
Which exams ask Solids MCQs?
Solids and crystal structure questions appear in MDCAT, ECAT, NUMS and AKU entry tests and in FSc board exams in Pakistan. In Bangladesh, the topic is studied in HSC chemistry and helps with the medical admission test.
Why are amorphous solids called supercooled liquids?
Amorphous solids such as glass have a disordered arrangement of particles similar to a liquid, but they are rigid because the particles cannot move freely. They have no sharp melting point and soften gradually on heating, so they are sometimes described as supercooled liquids.
Last reviewed October 2026