This question is about the halogens - AQA - GCSE Chemistry - Question 8 - 2020 - Paper 1

The boiling points of the halogens increase down the group. This is primarily due to increasing molecular size and relative molecular mass, which leads to stronger intermolecular forces (London dispersion forces) between the molecules. As the size of the molecules increases, more energy is required to overcome these intermolecular forces and convert the substance from a liquid to a gas.

Boiling point is a bulk property, which means it refers to the behavior of a large number of molecules rather than a single molecule. The boiling point indicates the temperature at which the vapor pressure of a liquid equals the atmospheric pressure, affecting many molecules and not just one.

The gas / halogen is toxic. Conducting the experiment in a fume cupboard prevents inhalation of harmful gases.

As we move down the group, the atoms have more electron shells. This means the outer electrons are further from the nucleus, leading to a decrease in attraction between the nucleus and the outer electrons. Consequently, it becomes more difficult for these atoms to gain an electron, resulting in decreased reactivity.

First, we calculate the moles of iron and chlorine:

• Moles of iron:

$\text{Moles} = \frac{\text{mass}}{\text{molar mass}} = \frac{4.48 \, g}{56 \, g/mol} = 0.08$

• Moles of chlorine:

$\text{Moles} = \frac{8.52 \, g}{35.5 \, g/mol} = 0.24$

Thus, the ratio is:

$\text{Fe : Cl} = 0.08 : 0.24 = 1 : 3.$

The balanced equation for the reaction, accounting for the stoichiometry derived from the previously calculated mole ratio, is:

$2 \, \text{Fe} + 3 \, \text{Cl}_2 \rightarrow 2 \, \text{FeCl}_3.$