(a)(i) A saturated solution is one that will dissolve no more of the solute at a particular temperatuie in the presence of excess solute.
(ii) Solubility is the,maximum amount of solute (number of moles/mass) that dissolves in 1dm\(^3\) of solvent at a particular temperature.

(b) Mass of saturated solution = 17.85 — 7.16 = 10.69
Mass of dry salt = 9.30 — 7.16 = 2.14
Volume of solution = 10.69cm\(^3\)
Since volume of solution = \(\frac{mass}{density}\)
and density = 1.0g/dm\(^3\)
(i) Solubility in g/dm\(^3\)
10.69cm\(^3\) of solution Y contains 2.14g of salt Y
1cm\(^3\) of solution Y contains \(\frac{2.14 }{10.69}\)
1000cm\(^3\) = \(\frac{2.14 \times 1000}{10.69}\) = 200.19g/dm\(^3\)

(ii) Solubility in mol/dm\(^3\) = \(\frac{\text{solubility in g/dm}^3}{\text{molar mass of salt Y}}\)
= \(\frac{200.19}{100}\)
= 2.00 mol/dm\(^3\)
(c) NaCI — Ionic bond of electrovalent bond
CO\(_{2}\) — van der Waals forces
SiO — Covalent bond Al\(_{(s)}\) — Metallic bond.

(d)(i) Reactivity is due to loss of electrons, i.e the ease of electron loss, hence ionization energy decreases down the group.
(ii) Mg has more valence electrons contributing to the stronger binding energy compared to Na.
(iii) Potassium loses electron more readily than sodium, has lower ionization energy than sodium.

(e)(i) Isotopes are atoms of the same element with the same atomic number but different mass number.
(ii) Li = \(\frac{2 \times 6}{27}\) + \(\frac{25 \times 7}{27}\)
= 6.925