Explain the purpose of a thermometer in distillation and identify the collected liquid. Draw the dot and cross diagram for CO2.

Step 1: Answer question 16 (continued from previous image).

*c) The purpose of the thermometer is to measure the temperature of the vapour (or the boiling point of the liquid). This ensures that the liquid being collected is pure and helps to identify it.

*d) The liquid collected in the test tube is distilled water (or pure water).

Step 2: Answer question 17.

*a) Draw dot and cross diagram to show bonding in Carbon (IV) oxide ($\text{CO}_2$).
Carbon (C) has 4 valence electrons. Oxygen (O) has 6 valence electrons.
In $\text{CO}_2$, carbon forms two double covalent bonds with two oxygen atoms.

$$\text{O} = \text{C} = \text{O}$$

Each oxygen atom shares 2 electrons with carbon, and carbon shares 2 electrons with each oxygen atom. Each oxygen atom also has 2 lone pairs of electrons.
The dot-and-cross diagram for $\text{CO}_2$ is:

$$\text{O} \stackrel{\bullet\bullet}{\text{=}} \text{C} \stackrel{\bullet\bullet}{\text{=}} \text{O}$$

Where $\bullet$ represents electrons from carbon and $\times$ represents electrons from oxygen (or vice versa).
A more detailed representation:

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