Why are amorphous solids sometimes described as supercooled liquids?
Correct answer A. Their particles lack long-range order, like those of a liquid
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MDCAT ECAT Chemistry MCQs
Page 33 of MDCAT ECAT Chemistry multiple-choice questions with answers. Tap an option to check yourself.
Page 33 of 39
- 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
Which statement correctly describes a reversible reaction that has reached dynamic equilibrium in a closed vessel?
Correct answer B. The forward and reverse reactions continue at equal rates
For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), what is the effect of increasing the total pressure at constant temperature?
Correct answer B. The equilibrium shifts to the right because fewer gas molecules are on that side
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What is the effect of adding a catalyst to a reaction mixture at equilibrium?
Correct answer C. Equilibrium is reached sooner but its position and K are unchanged
Which property is typical of molecular crystals?
Correct answer B. They are soft and have low melting points
Which of the following forms a molecular crystal?
Correct answer D. Iodine, I₂
Why are ionic crystals brittle?
Correct answer B. Shifting a layer brings ions of like charge next to each other, causing repulsion
Lattice energy is the energy released when ____
Correct answer C. one mole of an ionic crystal is formed from its gaseous ions
Which compound has the highest lattice energy?
Correct answer A. MgO
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Which sodium halide has the lowest lattice energy?
Correct answer A. NaI
Why does MgO have a much higher melting point (about 2850 °C) than NaCl (801 °C)?
Correct answer D. The higher ionic charges in MgO give a much larger lattice energy
Lattice energy of an ionic compound is usually determined by ____
Correct answer C. an indirect calculation using the Born–Haber cycle
How many NaCl formula units are present in one cubic unit cell of sodium chloride?
Correct answer A. 4
Which property is characteristic of crystalline solids?
Correct answer B. They have sharp melting points
Crystalline solids show different values of properties such as refractive index and electrical conductivity in different directions. This property is called ____
Correct answer C. anisotropy
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Which of the following is an amorphous solid?
Correct answer C. Glass
A crystal lattice is best described as ____
Correct answer D. a regular three-dimensional arrangement of points representing the particles of a crystal
The smallest repeating unit which, when repeated in three dimensions, generates the whole crystal lattice is called the ____
Correct answer D. unit cell
How many crystal systems are used to classify crystals?
Correct answer A. Seven
Which set of unit cell parameters describes the cubic crystal system?
Correct answer D. a = b = c and α = β = γ = 90°