IB DP Chemistry Mock Exam SL Paper 1B Set 4 - 2025 Syllabus
IB DP Chemistry Mock Exam SL Paper 1B Set 4
Prepare for the IB DP Chemistry Exam with our comprehensive IB DP Chemistry Exam Mock Exam SL Paper 1B Set 4. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam
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