7(a) Describe what is seen when chlorine water is added to potassium bromide solution and the mixture shaken - Edexcel - GCSE Chemistry - Question 7 - 2018 - Paper 1

In the reaction, chlorine ($Cl_2$) gains electrons to form chloride ions ($Cl^-$). The half-equation for the reduction of chlorine can be represented as:

$Cl_2 + 2e^- → 2Cl^-$

Here, each chlorine atom in $Cl_2$ gains an electron, indicating a reduction process, as reduction involves the gain of electrons.

The half-equation for the formation of bromine from bromide ions is:

$2Br^- → Br_2 + 2e^-$

In this equation, two bromide ions lose electrons to form one molecule of bromine.

The balanced equation for the reaction is:

$2Al + 3Cl_2 → 2AlCl_3$

This equation shows two moles of aluminum reacting with three moles of chlorine gas to produce two moles of aluminum chloride.

A simple experiment to demonstrate the presence of charged particles in the solution involves using a conductivity test. Connect a battery to two electrodes immersed in the ionic solution.

If charged particles (ions) are present, the circuit will complete, and a bulb connected in the circuit will light up. This indicates the movement of ions, confirming the presence of charged particles in the solution.