This question is about magnesium and magnesium chloride - AQA - GCSE Chemistry - Question 5 - 2016 - Paper 2

Magnesium chloride must be either molten or dissolved in water because, in solid form, the ions are held in a fixed lattice structure and cannot move freely. When melted or dissolved, the ions are free to move, allowing them to carry electric charge and conduct electricity required for the electrolysis process.

At the negative electrode, magnesium ions (Mg²⁺) are attracted due to the electrolysis process. As these positively charged ions approach the negative electrode, they gain electrons and are reduced. Specifically, each magnesium ion gains two electrons, converting it back into elemental magnesium. The half-reaction can be represented as:

$\text{Mg}^{2+} + 2e^- \rightarrow \text{Mg}$

The gas produced at the negative electrode in Experiment 2 is hydrogen (H₂).

Magnesium is not produced at the negative electrode in Experiment 2 because hydrogen ions (H⁺) from the water are more readily reduced than magnesium ions. Since hydrogen is higher in the activity series, it takes precedence, leading to the generation of hydrogen gas instead of magnesium.

The balanced half equation for the reaction at the positive electrode is:

$2 \text{Cl}^- \rightarrow \text{Cl}_2 + 2e^-$

Metals can be bent and shaped due to the presence of metallic bonding, which allows layers of atoms to slide over each other without breaking the metallic structure. The delocalized electrons in metals give them the ability to conduct electricity and maintain structural integrity while allowing flexibility, enabling metals to be easily molded into various shapes.