Chemical Bonding

The structure of the hormone histamine is shown.

Which row contains the bond angles $x$, $y$ and $z$ in histamine in the correct order from the smallest to the largest?

Options

Propene, hydrogen cyanide and carbon dioxide each contain $\pi$ bonds.

Which molecules contain two $\pi$ bonds?

Options

A   carbon dioxide and hydrogen cyanide
B   carbon dioxide and propene
C   hydrogen cyanide and propene
D   hydrogen cyanide only

Which graph correctly describes a trend found in Group 17?

[X represents a halogen atom.]

Options

What is the total number of $\text{sp}^3$ hybridised atomic orbitals used in the bonding of but-2-ene?

Options

A   2
B   4
C   6
D   8

Which diagram represents the lattice structure of sodium chloride?

Options

A   Diagram A
B   Diagram B
C   Diagram C
D   Diagram D

In which pair do both species:

• have the same shape
• have the same number of covalent bonds?

Options

A   methane and the ammonium ion
B   carbon dioxide and nitrogen
C   boron trifluoride and ammonia
D   water and oxygen

A reaction involving ammonium ions is shown.

$$\text{NH}_4^+ + \text{OH}^- \rightleftharpoons \text{NH}_3 + \text{H}_2\text{O}$$

Four statements about this reaction are listed.

1. The ammonium ions are reduced.
2. In the reverse reaction, ammonia acts as a Brønsted–Lowry base.
3. The ammonium ion and the ammonia molecule have the same bond angle.
4. This reaction is not a redox reaction.

Which statements are correct?

Options

A   1 and 2
B   1 and 3
C   2 and 4
D   3 and 4

Consider the following statements.

1 Silicon dioxide has a higher melting point than sulfur dioxide.
2 Ammonia has a higher boiling point than phosphine, PH₃.

Which statements are correct?

Options

A   both statement 1 and statement 2
B   statement 1 only
C   statement 2 only
D   neither statement 1 nor statement 2

Which row is correct?

Options

The average intermolecular forces in water are much stronger than the average intermolecular forces in steam.

The average intermolecular forces in ice are slightly stronger than the average intermolecular forces in water.

Enthalpy changes are associated with the equilibrium processes shown.

$$\begin{aligned} \text{H}_2\text{O(l)} &\rightleftharpoons \text{H}_2\text{O(g)} \quad \Delta H_\text{b} \\ \text{H}_2\text{O(s)} &\rightleftharpoons \text{H}_2\text{O(l)} \quad \Delta H_\text{m} \end{aligned}$$

Which statements are correct?

1 $\Delta H_\text{b}$ and $\Delta H_\text{m}$ are both negative.
2 $\Delta H_\text{b}$ is greater than $\Delta H_\text{m}$.
3 The intermolecular forces in ice and water are of the same type.

Options

A   1, 2 and 3
B   1 and 2 only
C   1 and 3 only
D   2 and 3 only