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The pH of two solutions, X and Y, were measured before and after 10 drops of concentrated NaOH was added to each - HSC - SSCE Chemistry - Question 23 - 2023 - Paper 1
Question 23
The pH of two solutions, X and Y, were measured before and after 10 drops of concentrated NaOH was added to each. Solution X Initial pH = 7.00 Final pH = 12.00 Sol... show full transcript
Worked Solution & Example Answer:The pH of two solutions, X and Y, were measured before and after 10 drops of concentrated NaOH was added to each - HSC - SSCE Chemistry - Question 23 - 2023 - Paper 1
Step 1
Explain the pH changes that occurred in both solutions
Answer
When NaOH was added to solution X, a strong base, it led to a significant increase in pH from 7.00 to 12.00. This occurs because NaOH dissociates completely in solution, releasing OH⁻ ions which react with H⁺ ions, causing a marked increase in pH, as per the relationship:
In contrast, solution Y exhibited little change in pH, moving from 7.00 to 7.02. This minimal change suggests that solution Y acts as a buffer, maintaining stable pH despite the addition of NaOH. This indicates that the components in solution Y are able to react with the OH⁻ ions added, thus preventing the significant change in pH observed in solution X.