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The 2025 updates to the IB Chemistry syllabus might leave students uncertain about the new Paper 2 format. In this post, we'll simplify everything you need to know, helping you tackle the exam with confidence and clarity.
IB Chemistry Paper 2
- Accounts for 44% of the student's subject grade (SL & HL).
- SL students have 1 hour 30 minutes, while HL students are given 2 hours 30 minutes to complete Paper 2.
- Calculators are permitted.
- Paper 2 is made up of short-answer and extended-response questions.
- Paper 2 may cover all topics of the syllabus.
- A calculator is required for this exam.
- Students will have access to an IB-issued formula booklet.
A typical SL question may look the following way:
Hydrochloric acid is an important chemical reactant and industrial chemical.
(a) A pH probe is placed in a small volume of 0.10 mol dm-3 solution of hydrochloric acid. The pH is recorded while a steady stream of distilled water is added to the acid at constant temperature.
(i) On the axes, sketch the graph of pH against volume of water added [3]
(ii)The experiment is repeated using 0.10 mol dm-3 ethanoic acid at the same temperature. Calculate the initial pH of the ethanoic acid [2]
pKa ethanoic acid = 4.76
(b) Chloride ions can form complex ions with some transition metals. The formulas and colours of three compounds of cobalt are:
[Co(NH3)6]Cl3 → orange-yellow
[Co(NH3)5Cl]Cl2 → purple
[Co(NH3)4Cl2]Cl → green
(i) Deduce the oxidation state of cobalt in [Co(NH3)5Cl]Cl2 and the charge of the complex ion. [2]
(ii) Describe the bonding of chloride ions in [Co(NH3)4Cl2]Cl. [2]
(iii) Explain why these complex ions are coloured. [3]
(iv) State and explain, in which of the complex ions, the electron transitions responsible for the colour require the highest energy. Use the colour wheel and the electromagnetic spectrum in sections 5 and 15 of the data booklet. [2]
A typical HL question may look the following way:
(a) Halogens are important reactants in the laboratory and in the environment.
(i) Write an equation for the homolytic fission of chlorine under UV light, showing the movement of electrons. [2]
(ii) Under different conditions, chlorine molecules can break down by heterolytic fission. Write an equation showing the movement of electrons. [1]
(iii) Identify, giving a reason, which one of the three species produced in (i) and (ii) is an electrophile. [1]
(iv) Draw the full structural formula of the most stable carbocation formed in the reaction between hydrogen chloride and propene. [1]
(v) Outline why this intermediate is the most stable. [1]
(b) The graph shows the boiling points of the first five straight-chain primary alcohols and fluoroalkanes.
(i) Outline why the alcohols have higher boiling points than fluoroalkanes of similar relative formula mass. [1]
(ii) Explain the general trend in the boiling points shown for the alcohols. [2]
(iii) Predict, giving a reason, how the boiling points of branched fluoroalkanes compare to their straight-chain isomers. [1]
(iv) Explain why primary bromoalkanes have higher boiling points compared to the corresponding fluoroalkanes. [1]
(c)
(i) Draw the structures of 2-bromobutane and its tertiary isomer. [2]
(ii) One of the isomers in (i) exists as enantiomers. Draw their stereochemical formulas. [1]
(iii) The IR and 1H NMR spectra of 2-bromobutane are shown. Circle the regions which indicate the presence of the bromine atoms. Use sections 20 and 21 of the data booklet. [2]
(iv) Explain whether the IR and 1H NMR spectra can be used to distinguish the tertiary isomer from 2-bromobutane. [2]
How to succeed in Chemistry Paper 2?
To excel in Chemistry Paper 2, you need a solid understanding of key concepts and strong problem-solving skills. Be sure to thoroughly study all topics as the exam can include any area of the syllabus. IB Chemistry focuses heavily on the application of concepts, so simply memorizing information is not enough. It’s essential to have a deep understanding of the material, approach it from different angles, and apply it in a variety of contexts. Hence, we strongly advise practicing past exam questions to master these problem-solving skills and be prepared for the real exam.
We hope you found this post helpful. For more useful materials associated with the IB check out the wide variety of IA, EE and TOK exemplars available at Clastify.
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