Explanation:
The student must recognise that the described technique is IR spectroscopy, and correctly interpret the diagram to identify a wavelength in the IR range.
The question is of moderate difficulty as it requires both the definition and the diagram to be understood correctly.

Explanation:​
The air is naturally composed of 0.04% carbon dioxide, which dissolves in water to form the weak carbonic acid

Explanation:​
Group 2 metal oxides produce alkaline metallic hydroxides when dissolved in water.

Metalloids lie on the boundary between metals and non-metals in the p block of the periodic table. They are shiny like metals but brittle like non-metals, and can switch between being electrical insulators and electrical conductors. Although this switchable conductivity could be considered as a change from metal-like to non-metal-like behaviour, it does not affect all properties of the element: the element does not switch from being a metal to a non-metal.

Metalloids do not contain incomplete d subshells (this is a property of transition metals) and lie alongside the poor metals in the p block of the periodic table. This question is categorised as moderately difficult as the concept of metalloids is not covered extensively in the syllabus, though the distinction between metals, non-metals and metalloids is highlighted.

Explanation​:
Saturated compounds contain only single bonds.
Butyne is an alkyne, and so, has a triple bond.

Explanation:​

Lithium is in group 1 and so forms Li^+ ions. The formula of the nitride ion is N^3−as nitrogen is in group 15. For the positive and negative charges to cancel out, three Li+ ions are needed for each N3− ion.

Explanation​:
Structural isomers have the same molecular formula but different structural formulae.
Methoxyethane and propanol both have the molecular formula C3H8O.

Explanation:​
The 6 protons in the nucleus of carbon will exert a stronger attractive force on the second energy level electrons than the 5 protons of boron.
Increasing electron affinity from left to right across a period.

Explanation:
The student must recognise that there are three proton environments in a 3:2:3 ratio;
B has only $2$ environments ($3:2$ ratio), while C has 4 (3:2:2:1). D has $3$ environments but they are in a 6:1:1 ratio.
The question is hard as two pieces of information must be extracted from the spectrum and interpreted in the context of the structural formulas given.

Explanation:​
In HBrO, the oxidation states of both H and Br are +1.

Explanation​:
The electron configuration of Zn2+ is [Ar] 3d^10. There are no vacancies in the $d$ subshell so a transition between the split energy levels of the octahedral complex is not possible.
This question is categorized as easy as the colourless nature of d10 ions is covered explicitly in the syllabus.

Explanation​:
Increasing atomic radius results in a weaker electrostatic force of attraction between the nucleus and electrons in the covalent bond. An increased number of shells down the group increases the shielding between the nucleus and electrons in the covalent bond.

Explanation:​

The group of an element is determined by its atomic number, which is found in the lower left corner of the element symbol. Although this conflicts with the representation in the data booklet, students should be able to differentiate between the mass and atomic number based on their relative size. The elements represented by options A, B, C and D are calcium (an alkaline earth metal), iron (a transition metal), gallium (a poor / p block metal) and rubidium (an alkali metal), respectively. This question is moderately difficult as the student must identify the correct value from the given symbol and relate it to the position of an element in the periodic table.

Explanation​:
1 and 2 are enantiomers, exhibiting opposite optical activities (rotate plane polarised light in opposite directions by the same amount).
Compound 3 is achiral, so it has a rotation angle of 0 degrees.
This question is in the “hard” category, as the student must be able to determine a molecule's chirality and recall how polarimetry can be used to distinguish between stereoisomers.

Explanation:
Ethers contain C−O single bonds $\text{not}$ the $\mathrm{C}=\mathrm{O}$ carbonyl group.

Explanation:​
Acid rain is formed from sulfur and nitrogen oxides dissolving in the clouds.

Explanation​:
The longest carbon chain has 5 carbons and will include the C=C.
The alkene is given priority and is on carbon-1.
The methyl group is bonded to carbon-2.

Explanation:​

The names of the labelled groups are covered explicitly in the syllabus.

Explanation:
NH2 is the amine functional group, RCOOR′ is the ester functional group.

Explanation​:
The overall charge on the complex ion is $1-$, water is neutral and the chloride ion has a charge of $1-$ = $+$ Cr.
Cr has an oxidation state of 3+.

Explanation:​
Atomic radius and metallic character decrease across a period. Ionization energy decreases down a group due to increased shielding.

Explanation:​
Choices III and IV are ethene and ethyne with a double bond and a triple bond, respectively. They belong to the classes of alkenes and alkynes, which can be deduced by the general formulae, CnH2n and CnH2n−2​​ .
Choice I is the alkane methane, and choice II is a halogenoalkane (chloromethane).