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Cobalt(II) chloride solution changes colour when an excess of concentrated hydrochloric acid is added - AQA - A-Level Chemistry - Question 20 - 2022 - Paper 3
Question 20
Cobalt(II) chloride solution changes colour when an excess of concentrated hydrochloric acid is added. What type of reaction takes place?
Worked Solution & Example Answer:Cobalt(II) chloride solution changes colour when an excess of concentrated hydrochloric acid is added - AQA - A-Level Chemistry - Question 20 - 2022 - Paper 3
Step 1
What type of reaction takes place?
Answer
When excess concentrated hydrochloric acid is added to cobalt(II) chloride solution, a ligand substitution reaction occurs. In this process, the water ligands in the cobalt(II) chloride complex are replaced by chloride ions from the hydrochloric acid, leading to a change in color of the solution. The resulting compound is a cobalt(II) chloride complex with chloride ions as ligands, which typically appears more blue than the original pink hue of cobalt(II) chloride.