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 this state, the ions are free to move. In a solid state, the ions are fixed in a lattice structure, preventing them from conducting electricity. When molten or dissolved, the ions can move freely towards the electrodes, allowing the electrolysis process to occur.

At the negative electrode, magnesium ions (Mg²⁺) are attracted to the electrode, where they gain two electrons. This reduction process transforms the magnesium ions into neutral magnesium metal. The half-equation can be represented as:

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

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 is more reactive than magnesium. Therefore, during electrolysis, hydrogen ions (H⁺) from the water are preferentially reduced over magnesium ions, resulting in the production of hydrogen gas instead of magnesium.

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

$2Cl^- \rightarrow Cl_2 + 2e^-$

Metals can be bent and shaped because of the arrangement of their particles, which are found in layers. These layers of atoms can slide over one another when a force is applied, allowing the metal to deform without breaking. This property, known as malleability, is a result of the metallic bonds, which do not hold the layers rigidly in place.