Define the term first ionization energy.

Explain why the first ionization energy of magnesium is higher than that of sodium.

calcium has a higher melting point than potassium.

sodium oxide has a higher melting point than sulfur trioxide.

Define the terms acid and base according to the Brønsted-Lowry theory and state one example of a weak acid and one example of a strong base.

Describe two different methods, one chemical and one physical, other than measuring the pH, that could be used to distinguish between ethanoic acid and hydrochloric acid solutions of the same concentration.

Black coffee has a pH of 5 and toothpaste has a pH of 8. Identify which is more acidic and deduce how many times the \({\text{[}}{{\text{H}}^ + }{\text{]}}\) is greater in the more acidic product.

Samples of sodium oxide and sulfur trioxide are added to separate beakers of water. Deduce the equation for each reaction and identify each oxide as acidic, basic or neutral.

the amount of energy required to remove one (mole of) electron(s);

from (one mole of) an atom(s) in the gaseous state;

greater positive charge on nucleus / greater number of protons / greater core charge;

greater attraction by Mg nucleus for electrons (in the same shell) / smaller atomic radius;

calcium ionic charge is twice/greater than the potassium ionic charge / calcium has more delocalized electrons than potassium;

greater attraction of delocalized electrons and \({\text{C}}{{\text{a}}^{2 + }}\) / less attraction between the delocalized electrons and \({{\text{K}}^ + }\);

Do not accept calcium ion has a 2⁺ without comparison to \({{\text{K}}^ + }\).

Na2O ionic/(stronger electrostatic) attractions between \({\text{N}}{{\text{a}}^ + }\) and \({{\text{O}}^{2 - }}\);

\({\text{S}}{{\text{O}}_{\text{3}}}\) has (weak) intermolecular/van der Waals’/London/dispersion/dipoledipole attractions;

intermolecular/van der Waals’/London/dispersion/dipole-dipole forces are weaker/more easily broken than (strong) ionic bonds / ionic bonds are stronger/harder to break than intermolecular bond/van der Waals’/London/dispersion/dipole-dipole forces;

acid is a proton/\({{\text{H}}^ + }\) donor and base is a proton/\({{\text{H}}^ + }\) acceptor;

\({{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\)/\({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\) and NaOH/KOH/\({\text{Ba(OH}}{{\text{)}}_{\text{2}}}\);

Accept any suitable examples.

Chemical

reaction with reactive metal/Mg/Zn/carbonate/hydrogen carbonate;

hydrochloric acid would react faster/more vigorously / ethanoic acid would react slower/less vigorously;

OR

react with alkali;

temperature change will be more for hydrochloric acid / temperature change will be less for ethanoic acid;

Physical

conductivity;

hydrochloric acid will conduct more/higher / ethanoic acid will conduct less/lower;

Accept other suitable examples.

black coffee;

\({\text{1}}{{\text{0}}^{\text{3}}}\)/1000 times;

\({\text{N}}{{\text{a}}_{\text{2}}}{\text{O(s)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}} \to {\text{2NaOH(aq)}}\);

\({\text{S}}{{\text{O}}_3}{\text{(l)}} + {{\text{H}}_2}{\text{O(l)}} \to {{\text{H}}_2}{\text{S}}{{\text{O}}_4}{\text{(aq)}}\);

Ignore state symbols.

\({\text{N}}{{\text{a}}_{\text{2}}}{\text{O}}\): basic and \({\text{S}}{{\text{O}}_{\text{3}}}\): acidic;

The definition of first ionisation energy given by most candidates in (a) (i) was incomplete. The word gaseous was missing from most definitions given.

Candidates also struggled to explain the differences in first ionization energies of magnesium and sodium. Candidates did not need knowledge of subshells as was suggested in one comment in the G2 forms. Candidates needed to make reference to nuclear charge and size of atomic radius and their effect on the attraction to the electrons.

Part (b) (i) clearly indicated that candidates were not familiar with metallic bonding.

In part (ii) the candidates incorrectly discussed the bonding in the sulfur trioxide molecule rather than the intermolecular forces. Many candidates incorrectly wrote words to the effect that ionic bonding was stronger than covalent bonding to explain the differences in melting point of the two compounds.

Parts (c) (i) and (iii) were well managed with candidates correctly defining acids and bases according to the Brønsted-Lowry theory and had a good understanding of the relationship between pH and concentration of \({{\text{H}}^ + }\) ions.

Part (c) (ii) was reasonably well answered but candidates did not always provided one chemical and one physical method to distinguish between the two acids.

Even though candidates were able to identify sodium oxide and sulfur trioxide as basic and acidic respectively they struggled to write correct equations for the oxides with water in part (d).