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Question
A sample of rain water turned universal indicator paper yellow. What would you expect it pH to be? Is it a strong or a weak acid?
Solution
A universal indicator shows a greenish-yellow colour for pH 6 and orange yellow for pH 5. This means that if the indicator turns yellow, the pH should be between these two values. Hence, it must have a pH value between 5 and 6. As the pH is closer to 7 (between 5 and 6), it is a weak acid.
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