JAMB - Chemistry (2025 - No. 49)
In a series of solutions with pH of 2.5, 3.5, 7.0 and 8.0, which is likely to turn red moist litmus paper blue?
3.5
8.0
2.5
7.0
Explanation
The solution with a pH of 8.0 is likely to turn red moist litmus paper blue, which corresponds to option B.
Litmus paper is an indicator used to test for acidity or basicity:
Acids (pH below 7) turn blue litmus paper red. The solutions with pH 2.5 and 3.5 are acidic.
Bases (pH above 7, or alkaline) turn red litmus paper blue. The solution with pH 8.0 is basic.
Neutral solutions (pH exactly 7.0) cause no color change in either red or blue litmus paper.
Bases turn red litmus paper blue.Therefore, only the basic solution (pH 8.0) will turn red litmus paper blue.
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