Free Solids MCQs with Answers

• A. has a long range ordered arrangement of particles and a sharp melting point
• B. has no definite shape
• C. softens gradually over a range of temperature
• D. is always transparent

Explanation: In a crystal every particle occupies a regular repeating position, so all the bonds are identical and break at one definite temperature…

• A. isomorphism
• B. anisotropy
• C. polymorphism
• D. allotropy

Explanation: Because the arrangement of particles differs along different axes of a crystal, properties measured along those axes differ too, and this…

• A. isomers
• B. isotopes
• C. allotropes
• D. isomorphs

Explanation: Allotropes are different structural forms of the same element in the same physical state, and here diamond is a rigid three dimensional…

• A. simple cubic
• B. hexagonal
• C. body centred cubic
• D. face centred cubic

Explanation: Sodium chloride crystallises in a face centred cubic arrangement in which each sodium ion is surrounded octahedrally by six chloride ions…

• A. the number of oppositely charged ions immediately surrounding it
• B. the charge on the ion
• C. the number of unit cells it belongs to
• D. the number of electrons it has lost or gained

Explanation: Coordination number counts the nearest neighbours of opposite charge, so it is six in sodium chloride and eight in caesium chloride, the…

• A. their ions are held by weak van der Waals forces
• B. strong electrostatic forces act between oppositely charged ions throughout the lattice
• C. they contain covalent bonds between the ions
• D. the ions are free to move at room temperature

Explanation: Every ion attracts all the oppositely charged ions around it, and a great deal of energy is needed to break this extended three…

• A. the covalent bonds within the molecules are weak
• B. they contain no bonds at all
• C. only weak intermolecular forces have to be overcome on melting
• D. their molecules are very heavy

Explanation: Melting separates molecules from one another, and in a molecular crystal they are held only by dispersion forces or dipole interactions…

• A. Ice
• B. Sodium chloride
• C. Solid carbon dioxide
• D. Diamond

Explanation: In diamond every carbon is covalently bonded to four others in a continuous three dimensional network, so melting it means breaking…

• A. unit cell
• B. crystal face
• C. lattice point
• D. domain

Explanation: Stacking the unit cell repeatedly in three dimensions generates the entire crystal, so knowing its dimensions and contents describes the…

• A. four
• B. seven
• C. fourteen
• D. twenty

Explanation: There are seven crystal systems, defined by the relative lengths of the unit cell axes and the angles between them, the cubic system being…

• A. needed to melt one mole of an ionic solid
• B. needed to vaporise one mole of a liquid
• C. released when one mole of an ionic crystal is formed from its gaseous ions
• D. absorbed when an electron is added to a gaseous atom

Explanation: Bringing gaseous ions together into an ordered lattice releases a large amount of energy, so lattice energy is strongly exothermic and is…

• A. the charges on the ions increase and their radii decrease
• B. the charges on the ions decrease
• C. the ions become larger
• D. the compound is dissolved in water

Explanation: Electrostatic attraction is proportional to the product of the charges and inversely proportional to the distance between the ion centres…

• A. NaCl
• B. KCl
• C. MgO
• D. KBr

Explanation: Magnesium oxide is built from doubly charged Mg2+ and O2- ions that are also small, so both factors in the electrostatic expression work…

• A. melting converts the ions into atoms
• B. the ions become free to move only when the lattice breaks down
• C. electrons are released on melting
• D. the molten salt contains water

Explanation: Conduction in an ionic compound needs mobile charge carriers, and in the solid the ions are locked in fixed lattice positions even though…

• A. polymorphic
• B. allotropic
• C. isomorphic
• D. anisotropic

Explanation: Isomorphous substances such as potassium sulphate and potassium chromate crystallise in the same shape because their ions are of similar…

• A. each carbon forms four single covalent bonds
• B. the carbon atoms are ionised
• C. the layers are held by strong covalent bonds
• D. each carbon uses only three of its four valence electrons in bonding, leaving one delocalised

Explanation: In graphite each carbon is bonded to three others in a flat hexagonal sheet, and the fourth electron is delocalised between the layers, so…

• A. the mass of its particles
• B. the strength of the forces holding its particles together
• C. the size of its crystals
• D. its electrical conductivity

Explanation: Melting requires enough thermal energy to overcome the forces locking the particles in the lattice, so covalent network and ionic solids…

• A. their atoms are held in rigid directional covalent bonds
• B. they contain no free electrons
• C. layers of positive ions can slide over one another while the sea of delocalised electrons holds them together
• D. their ions are held by hydrogen bonds

Explanation: Metallic bonding is non directional, so displacing one layer of cations does not break the structure because the delocalised electrons…

• A. measures lattice energy directly in a calorimeter
• B. applies Hess's law to relate lattice energy to quantities that can be measured
• C. predicts the shape of the crystal
• D. measures the melting point of the ionic solid

Explanation: Lattice energy cannot be measured in an experiment, so the cycle links it to the enthalpy of atomisation, ionisation energy, electron…

• A. Solid iodine
• B. Sodium chloride
• C. Diamond
• D. Copper

Explanation: Iodine molecules are non polar, so the only attraction between them is the temporary induced dipole interaction known as the dispersion…