Explanation​:
Recall that the functional group is carboxyl and the class or series is carboxylic acid.

Explanation:​
Na^+, Ne, O^2−have 10 electrons in two energy levels with 11, 10, and 8 protons respectively. The increased number of protons has a greater pull on the 10 electrons and reduces the radius.
Ca^2+ has 18 electrons in 3 energy levels and is therefore, the largest.

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

Explanation​:
Statement II is incorrect as acids produce solutions with $\mathrm{pH}$ lower than 7.

Explanation:​
Across the same period, metals have lower ionization energies than non-metals due to lower nuclear charges with the same number of shells (shielding effect).

Explanation:​

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

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 N^3− ion.

Explanation​:
The number of shells and therefore the shielding effect is the same for all of these species.
As the number of protons decreases, the attraction between the nucleus and electrons decreases, resulting in a smaller radius.
K^+ has the most protons (19), whereas S^2− has the least (16).

Explanation​:
The two compounds are part of a homologous series because they have the same functional group but different hydrocarbon chains. Both compounds are alcohols, so interact via hydrogen bonding.
The CH2​ and CH3 groups of the alkyl chains, however, interact via weaker dispersion forces, as they contain only non-polar bonds. Increasing the length of the alkyl chain does not affect the strength of hydrogen bonding, but the strength of the dispersion forces is increased. More heat energy is needed to separate molecules of Y, so the boiling point is higher.

Explanation​:
First ionization energy decreases down a group due to increased shielding (number of shells). Beryllium must therefore have a higher first IE than magnesium. And similarly, oxygen higher than sulfur.
First ionization energy increases across a period due to increased nuclear charge for the same number of shells. Hence, oxygen has higher first IE than beryllium.

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

Explanation​:
The molecular formula of pentan-2-one is C5H10O

There are 5 C atoms and 10 H atoms, so the combustion produces 5115​ = 5 moles of CO2​ and 102210​ = 5 moles of H2O per mole of pentan-2-one. The value of b is therefore 5.0.

There are $15$ O atoms on the right-hand side of the equation but only 1 O atom in petan-2-one, so the compound must react with (15−1)/2​ = 7 moles of O2​. The value of a is therefore 7.0.

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

Explanation:​
The attraction for a shared pair of electrons in a covalent bond depends on electronegativity. Carbon has the lowest electronegativity value of the given elements across period 2, it has the lowest effective nuclear charge (least number of protons attracting valence electrons in energy level 2). Increasing electronegativity across a period from left to right.

Explanation:​

Elements in the same group (column) of the periodic table have the same number of outer shell (valence) electrons, represented by the group number; the number of electron shells increases down the group. Elements in the same row (period) have the same number of electron shells (or principal quantum number), equal to the period number; the number of valence electrons increases across the period. This question is moderately difficult as the student must recall multiple pieces of information and correctly interpret a schematic illustration of the periodic table.

Explanation:​
The oxidation state of X in choices A, B, and C is +3. The oxidation state of X in choice D is +6.

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

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

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:​
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).

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

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:​

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

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