Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
describe, in simple terms, the lattice structure of a crystalline solid which is: (a) giant ionic, including sodium chloride and magnesium oxide (b) simple molecular, including iodine, buckminsterfullerene \( C_{60} \) and ice (c) giant molecular, including silicon(IV) oxide, graphite and diamond (d) giant metallic, including copper
(a) describe hydrogen bonding, limited to molecules containing N–H and O–H groups, including ammonia and water as simple examples (b) use the concept of hydrogen bonding to explain the anomalous properties of H\(_2\)O (ice and water): • its relatively high melting and boiling points • its relatively high surface tension • the density of the solid ice compared with the liquid water
(a) describe covalent bonds in terms of orbital overlap giving σ and π bonds: - σ bonds are formed by direct overlap of orbitals between the bonding atoms - π bonds are formed by the sideways overlap of adjacent p orbitals above and below the σ bond (b) describe how the σ and π bonds form in molecules including H\(_2\), C\(_2\)H\(_6\), C\(_2\)H\(_4\), HCN and N\(_2\) (c) use the concept of hybridisation to describe sp, sp\(^2\) and sp\(^3\) orbitals
