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Show by means of an equilibrium equation the self-ionisation of water that occurs even in 'deionised' water. - Leaving Cert Chemistry - Question 1 - 2021
Question 1
Show by means of an equilibrium equation the self-ionisation of water that occurs even in 'deionised' water.
Worked Solution & Example Answer:Show by means of an equilibrium equation the self-ionisation of water that occurs even in 'deionised' water. - Leaving Cert Chemistry - Question 1 - 2021
Step 1
Show the equilibrium equation
Answer
In pure water, the self-ionization can be represented by the following equilibrium equation:
This equation indicates that two water molecules interact, resulting in the generation of hydronium ions (H₃O⁺) and hydroxide ions (OH⁻).
Explanation
Even in deionized water, which has had most of its ions removed, the self-ionization still occurs due to the inherent properties of water molecules. The equilibrium constant for this reaction at 25 °C is represented by the ion product constant of water, , calculated as:
This illustrates that even in the absence of added ions, water molecules can still dissociate and establish a dynamic equilibrium, albeit at a very low concentration of ions.