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ChemistryClass 123 marksmedium
The Solid State
Calculate the number of atoms present per unit cell in simple cubic, body-centred cubic (bcc) and face-centred cubic (fcc) structures.
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A corner atom is shared by 8 unit cells (contributes 1/8), a face atom by 2 (contributes 1/2) and a body-centre atom belongs entirely to one cell (contributes 1). Simple cubic: 8 corners x 1/8 = 1 atom. Body-centred cubic (bcc): (8 x 1/8) + 1 (centre) = 2 atoms. Face-centred cubic (fcc): (8 x 1/8) + (6 x 1/2) = 1 + 3 = 4 atoms.
Marking-scheme points
- ✓Corner atom contributes 1/8, face atom 1/2, body-centre 1
- ✓Simple cubic: 1 atom; bcc: 2 atoms
- ✓fcc: 1 + 3 = 4 atoms
ChemistryClass 123 markshard
The Solid State
An element with atomic mass 56 g/mol has a bcc structure with edge length 288 pm. Calculate its density. (NA = 6.022 x 10^23)
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For bcc, Z = 2. Edge a = 288 pm = 2.88 x 10^-8 cm, so a^3 = (2.88 x 10^-8)^3 = 2.39 x 10^-23 cm^3. Density d = Z M/(a^3 NA) = (2 x 56)/(2.39 x 10^-23 x 6.022 x 10^23) = 112/14.39 = 7.79 g/cm^3.
d = Z M/(a^3 NA)
Marking-scheme points
- ✓d = Z M/(a^3 NA); bcc Z = 2
- ✓a^3 = (2.88e-8)^3 = 2.39 x 10^-23 cm^3
- ✓d = 112/14.39 = 7.79 g/cm^3
ChemistryClass 123 marksmedium
Solutions
What are colligative properties? Name the four colligative properties.
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Colligative properties are those properties of a solution that depend only on the number of solute particles present and not on their chemical nature. The four colligative properties are: (1) relative lowering of vapour pressure; (2) elevation of boiling point; (3) depression of freezing point; and (4) osmotic pressure. They are used to determine the molar mass of a solute.
Marking-scheme points
- ✓Depend only on the number of solute particles, not their nature
- ✓Relative lowering of vapour pressure and elevation of boiling point
- ✓Depression of freezing point and osmotic pressure
ChemistryClass 123 markshard
Solutions
When 3 g of a non-volatile solute is dissolved in 100 g of water, the freezing point is depressed by 0.93 K. Calculate the molar mass of the solute. (Kf for water = 1.86 K kg/mol)
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Solutions
Calculate the osmotic pressure of a 0.1 M glucose solution at 300 K. (R = 0.0821 L atm K^-1 mol^-1)
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Electrochemistry
Calculate the standard EMF of a Daniell cell given the standard electrode potentials E(Cu2+/Cu) = +0.34 V and E(Zn2+/Zn) = -0.76 V.
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Electrochemistry
Write the Nernst equation for a general electrode and explain the terms.
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Electrochemistry
State Kohlrausch's law of independent migration of ions and give one application.
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Chemical Kinetics
Distinguish between order and molecularity of a reaction.
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Chemical Kinetics
Derive the integrated rate equation for a first order reaction.
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The p-Block Elements
Describe the Haber process for the manufacture of ammonia.
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The p-Block Elements
Describe the Contact process for the manufacture of sulphuric acid.
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The d- and f-Block Elements
How is potassium permanganate prepared from pyrolusite? State its oxidising action in acidic medium.
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Coordination Compounds
State the main rules for the IUPAC nomenclature of coordination compounds and name [Cu(NH3)4]SO4.
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Coordination Compounds
Name the main types of isomerism shown by coordination compounds.
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Coordination Compounds
Explain the geometry of a complex using valence bond theory. Distinguish inner and outer orbital complexes.
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Coordination Compounds
Explain the splitting of d orbitals in an octahedral crystal field according to crystal field theory.
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Haloalkanes and Haloarenes
How are haloalkanes prepared from alcohols? Write the reactions.
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Haloalkanes and Haloarenes
Distinguish between the SN1 and SN2 mechanisms of nucleophilic substitution.
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Alcohols, Phenols and Ethers
How are alcohols prepared by the hydration of alkenes and by the reduction of aldehydes and ketones?
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