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

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

Explanation:​

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

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

Explanation​:
Recall of transition metal properties.

Explanation:
The masses of options A, B, C and D are 29, 45, 31 and 28, respectively.
The mass of the fragment ion is 148 - 117 = 31, making option C correct.
This question is of moderate difficulty as two simple calculations are required

Explanation​:
The methyl groups are equivalent so produce one signal with integral 6, while the other protons both produce signals with integrals 1.
The student must recognise that all protons are detectable by NMR, including those attached to $\mathrm{O}$ atoms, and know how to count proton environments (COOH protons are sometimes too broad to detect due to proton exchange and/or hydrogen bonding, but this point is not covered at IB level).
The question is categorised as hard as several features of the $\mathrm{NMR}$ spectrum must be predicted.

Explanation:
NH3 has a non-bonding pair of electrons it can donate to a central metal ion. BH3 and CH4​ do not have non-bonding electrons.

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

Explanation​:
The charges of the positive and negative ions must cancel out to give an overall neutral compound. Group 2 metals form ions with a 2+ charge. The formulae of the counterions above are: $.$

Explanation​:
Each $\mathrm{Cl}$ ligand has a 1-charge.
2+(4x−1)=2−.
As outlined in the Chemistry Guide, [CuCl4]^2− has a tetrahedral shape.

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:​
C3H6​ belongs to the alkene class with the general formula CnH2n​, and has a three carbon chain.

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

Explanation​:
A tertiary amine is when three carbon groups are attached to the amine.

Explanation​:
There are 4 proton environments as the CH(CH3)2 protons are equivalent. Integration gives the relative number of protons in each environment. There are 3 on C1, 2 on C2, 1 of C3 and 6 on C4 and 5.

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

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​:
This question tests the ability of the student to convert a 3D model to wedge-dash notation.
The difficulty is low as the shape of the model is close to that of the 2D representation – no rotation around the single bonds is needed to determine the relative orientations of the substituent groups.

Carbon-1 is attached to an H-atom coming out of the page (wedge bond), an NH2​ group going into the page (dashed bond), and a CH3​ group in the plane of the page.
Carbon-2 is attached to a $\mathrm{Cl}$ atom coming out of the page (wedge bond), an H atom going into the page (dashed bond), and a CH3​ group in the plane of the page.

Explanation:​
First ionization energy is defined as the energy required to remove one mole of electrons from one mole gaseous atoms.

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

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 atomic number of Cr is higher than that of V by 1, and its relative atomic mass is also higher by approximately 1. The atomic number is unique for each element and dictates the position of the element in the periodic table; thus, Cr always has an atomic number of 24 and vanadium an atomic number of 23. However, isotopes of an element may have different atomic masses, so an atom of Cr may have a lower atomic mass than an atom of V. This question is categorised as easy since the difference between atomic number and atomic mass and the variation in mass between isotopes of an element are covered extensively in the syllabus.