Phenolphthalein
colourless
Which of the following substances will produce these results?
(A) Lemonade pH 2.9
(B) White wine pH 4.2
(C) Tap water pH 7.2 - HSC - SSCE Chemistry - Question 8 - 2060 - Paper 1
Question 8
Phenolphthalein
colourless
Which of the following substances will produce these results?
(A) Lemonade pH 2.9
(B) White wine pH 4.2
(C) Tap water pH 7.2
Worked Solution & Example Answer:Phenolphthalein
colourless
Which of the following substances will produce these results?
(A) Lemonade pH 2.9
(B) White wine pH 4.2
(C) Tap water pH 7.2 - HSC - SSCE Chemistry - Question 8 - 2060 - Paper 1
Step 1
Identify the pH range for Phenolphthalein
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Answer
Phenolphthalein is a pH indicator that is colourless in acidic solutions (pH < 7) and turns pink in alkaline solutions (pH > 8). Since the phenolphthalein remains colourless, the solution must be acidic.
Step 2
Evaluate the options based on pH
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Answer
We have three options:
Lemonade has a pH of 2.9, which is acidic, so it will keep phenolphthalein colourless.
White wine has a pH of 4.2, also acidic, thus phenolphthalein will remain colourless.
Tap water has a pH of 7.2, which is neutral and high enough to turn phenolphthalein pink.
Therefore, both lemonade and white wine are valid options. However, since the marking scheme indicates only one answer, the substance that is chosen typically is the one with the lowest pH.
Step 3
Conclusion
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Answer
Thus, the most suitable answer which corresponds to colourless phenolphthalein is (B) White wine, because it is also acidic but has a higher pH compared to lemonade.
