Which of the following is a chemical property of a substance?
A. Boiling point
B. Melting point
C. Reactivity with acid
D. Density
Answer: Option C
Solution (By JKSSB Mock Tests)
Chemical properties describe a substance's ability to undergo chemical changes—reactivity with acid, flammability, oxidation states, etc. Melting point, density, boiling point are physical properties that can be observed without changing composition. Reactivity with acid involves formation of new substances. A piece of magnesium reacting with HCl is a chemical change.
Explanation:
Synthetic detergents are primarily sodium salts of long-chain alkyl benzene sulphonic acids or alkyl hydrogen sulphates. Unlike soaps (which are carboxylate salts), detergents do not form insoluble precipitates with calcium and magnesium ions in hard water, making them effective cleansers.
Explanation:
Using Boyle's law: P₁V₁ = P₂V₂ => 2 atm × 5 L = 1 atm × V₂ => V₂ = 10 L. As pressure decreases, volume increases. The same mass of gas expands. This is a direct application of inverse proportionality. If temperature and amount of gas are constant, doubling pressure halves volume, etc.
Explanation:
In 2Na + Cl₂ → 2NaCl, sodium is oxidized (Na → Na⁺ + e⁻) and chlorine is reduced (Cl₂ + 2e⁻ → 2Cl⁻). It involves change in oxidation states. Options A and B are double displacement (no change in oxidation states). Option D is decomposition with no change in oxidation states (Ca: +2 remains +2). Redox reactions involve simultaneous oxidation and reduction.
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