100 mL of pure water at constant temperature is added to a 100 mL solution of 0.10 M NaOCl - VCE - SSCE Chemistry - Question 14 - 2004 - Paper 1
Question 14
100 mL of pure water at constant temperature is added to a 100 mL solution of 0.10 M NaOCl.
When the solution reaches equilibrium again, the
A. [H+] has decreased.
B... show full transcript
Worked Solution & Example Answer:100 mL of pure water at constant temperature is added to a 100 mL solution of 0.10 M NaOCl - VCE - SSCE Chemistry - Question 14 - 2004 - Paper 1
Step 1
A. [H+] has decreased.
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Answer
When pure water is added to a NaOCl solution, it dilutes the concentration of the NaOCl. This dilution increases the equilibrium concentrations of the species that dissociate, leading to a decrease in the concentration of hydrogen ions [H+]. Thus, statement A is true.
Step 2
B. pH of the solution has decreased.
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Answer
The addition of pure water dilutes the solution but does not add any acid. Therefore, the pH of the solution will tend to increase due to the decrease in [H+]. This means statement B is false.
Step 3
C. concentration of HOCl has increased.
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Answer
As the solution is diluted, the formation of HOCl (hypochlorous acid) is favored as per the equilibrium equation. Hence, the concentration of HOCl increases upon dilution, validating statement C as true.
Step 4
D. value of the equilibrium constant has halved.
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Answer
The equilibrium constant of a reaction is dependent only on temperature and not on the concentrations of the reactants or products. Therefore, the value of the equilibrium constant remains unchanged despite the dilution of the solution. Thus, statement D is false.
