A solution turns phenolphthalein pink. Which of the following could it be?
A. Hydrochloric acid
B. Lemon juice
C. Vinegar
D. Soap solution
Answer: Option D
Solution (By JKSSB Mock Tests)
Soap solution is basic, pH > 8.3, so it turns phenolphthalein pink. Lemon juice (citric acid) and vinegar (acetic acid) are acidic, pH < 7, phenolphthalein remains colorless. Hydrochloric acid is strongly acidic, colorless. Phenolphthalein indicator is colorless in acidic and neutral, pink in alkaline solutions. It is used in titrations.
Explanation:
Red litmus turning blue indicates that the solution is basic. Basic solutions have a pH greater than 7. Among the options, 10 is the only value greater than 7. pH 1 and 4 are acidic (turn blue litmus red), and 7 is neutral (no change in litmus color).
Explanation:
Concentrated sulfuric acid (H₂SO₄) has a very strong affinity for water and is widely used as a dehydrating agent in laboratories. It can remove water molecules from compounds, such as converting sugar (carbohydrate) to carbon, and is used to dry gases that do not react with it.
Explanation:
Graham's law of effusion/diffusion: Rate ∝ 1/√M (molar mass) at same temperature and pressure. Lighter gases diffuse faster. This is used in isotope separation (e.g., ²³⁵UF₆ vs ²³⁸UF₆) and in understanding gas behavior in leaks.
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