Question
The periodic table provides information about electron configuration, and physical and chemical properties of elements.
(a) Bismuth has atomic number 83. Deduce two pieces of information about the electron configuration of bismuth from its position on the periodic table.
(b) Outline why aluminium is malleable.
(c) An 11.98g block of pure aluminium was heated. Calculate the heat energy absorbed, in J, to increase its temperature from 18.0°C to 40.0°C. The specific heat capacity of aluminium is 0.902J \(g^{−1} K^{−1}\)
(d) Argon has three naturally occurring isotopes, \(^{36}Ar\), \(^{38}Ar\) and \(^{40}Ar\).
(i) Identify the technique used to determine the relative proportions of the isotopes of argon.
The isotopic composition of a sample of argon is 0.34% of \(^{36}Ar\), 0.06% of \(^{38}Ar\) and 99.6% of \(^{40}Ar\).
(ii) Calculate the relative atomic mass of this sample, giving your answer to two
decimal places.
(e) State the full electron configuration of the cobalt(II) ion, \(Co^{2+}\)
Answer/Explanation
Answer:
(a) Any two of:
«group 15 so Bi has» 5 valence electrons
«period 6 so Bi has» 6 «occupied» electron shells/energy levels
«in p-block so» p orbitals are highest occupied
occupied d/f orbitals
has unpaired electrons
has incomplete shell(s)/subshell(s)
(b) «layers of» cations slide over each other without disrupting bonding
OR
attraction between metal ions and delocalized electrons/metallic bonding is not
disrupted by changing position of metal ions
OR
metallic bonds are non-directional
OR
changing the shape does not disrupt the bonding
(c) «heat energy = 11.98 g x 0.902 J \(g^{−1} K^{−1}\) x 22.0 K =» 238 «J»
(d) (i) mass spectrometry
OR
mass spectroscopy
OR
mass spectrum
OR
MS
(ii) (0.0034 x 36) + (0.0006 x 38) + (0.996 x 40)
39.99
(e) \(1s^2\) \(2s^2\) \(2p^6\) \(3s^2\) \(3p^6\) \(3d^7\)
Question
The periodic table is a useful tool in explaining trends of chemical behaviour.
(a) (i) Annotate and label the ground state orbital diagram of boron, using arrows to represent electrons.
(ii) Sketch the shapes of the occupied orbitals identified in part (a)(i).
(b) Explain the decrease in first ionization energy from Li to Cs, group 1.
(c) (i) State the electron domain geometry of the ammonia molecule.
(ii) Deduce the Lewis (electron dot) structure of ammonia and sketch its 3D molecular shape.
(iii) Explain, with reference to the forces between molecules, why ammonia has a higher boiling point than phosphine (\(PH_3\)).
(d) (i) Ammonia is manufactured by the Haber process.
\(N_2 (g) + 3H_2 (g) \rightleftharpoons 2NH_3 (g)\) \(ΔH^{\theta}_t\) = – 92.0 kJ \(mol^{-1}\)
Outline what is meant by dynamic equilibrium.
(ii) Deduce the \(K_c\) expression for the reaction in part (d)(i).
(iii) The Haber process requires a catalyst. State how a catalyst functions.
(iv) Sketch a Maxwell–Boltzmann distribution curve showing the activation energies with and without a catalyst.
(v) Suggest how the progress of the reaction could be monitored.
Answer/Explanation
Answer:
(a) (i) 
(ii) 
(b) valence electron further from nucleus/«atomic» radius larger «down the group»
«electron» more shielded/ less attractive force/easier to remove
(c) (i) tetrahedral
(ii) 
(iii) ammonia has intermolecular/IMF hydrogen bonds «phosphine does not»
phosphine «and ammonia» dipole-dipole/London dispersion forces/instantaneous
dipole attractions/Van der Waals forces
hydrogen bonds stronger
(d) (i) «in a closed system» the rate of the forward reaction equals the rate of the reverse reaction.
(ii) \([NH_3]^2/([N_2][H_2]^3)\)
(iii) alternate pathway AND lowers activation energy/\(E_a\)
(iv) 
correct shape curve starting at the origin, without touching the x axis at high
energy.
(\(E_a\)) catalysed <(\(E_a\)) uncatalysed on x axis.
(v) change in AND
volume
OR
pressure
OR
temperature
OR
concentration of \(H_2\)/\(N_2\) /reactants/\(NH_3\) /product