A group of students produced a red solution by boiling red cabbage leaves in water - HSC - SSCE Chemistry - Question 7 - 2001 - Paper 1
Question 7
A group of students produced a red solution by boiling red cabbage leaves in water. When dilute sodium hydroxide was added to the solution, it turned purple. When di... show full transcript
Worked Solution & Example Answer:A group of students produced a red solution by boiling red cabbage leaves in water - HSC - SSCE Chemistry - Question 7 - 2001 - Paper 1
Step 1
Identify the Effect of Sodium Hydroxide
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Answer
When sodium hydroxide (a base) was added to the red cabbage solution, it turned purple. This indicates that the red cabbage indicator changes color in response to pH levels, with purple being a typical color in basic conditions.
Step 2
Analyze the Effect of Hydrochloric Acid
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Answer
The addition of dilute hydrochloric acid did not change the color of the red solution, suggesting that the solution remained in an acidic state, which does not affect the color of the red cabbage indicator.
Step 3
Determine Which Substance Causes Color Change
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Answer
To answer the question, we need to identify the likely pH change that each substance would cause:
(A) Cleaning solution containing ammonia is basic, likely turning the solution purple again.
(B) Concentrated hydrochloric acid is very acidic and may produce a distinct shift in color.
(C) Orange juice is also acidic but may not be strong enough to change the color significantly.
(D) Vinegar is acidic and might change the color depending on its concentration.
Given that a basic solution already changed the color, Option A (Cleaning solution containing ammonia) is the most likely to cause further color change.
