Soap is not suitable for washing in hard water because it forms:
A. Micelles
B. Soluble sodium salts
C. Insoluble calcium and magnesium salts (scum)
D. Foam
Answer: Option C
Solution (By JKSSB Mock Tests)
Soap (sodium carboxylate) reacts with Ca²⁺ and Mg²⁺ ions present in hard water to form an insoluble precipitate known as scum. This reduces lathering and wastage of soap. Synthetic detergents do not form scum because their calcium/magnesium salts are soluble.
Explanation:
Fractional distillation is specifically designed to separate miscible liquids whose boiling points differ by less than 25 K. It uses a fractionating column which provides surfaces for repeated evaporation and condensation, enriching the vapor with the more volatile component before it reaches the condenser.
Explanation:
KBr is ionic; potassium (metal) transfers one electron to bromine (non-metal) forming K⁺ and Br⁻. CO₂ and H₂O are covalent (sharing). Cl₂ is covalent (nonpolar).
Explanation:
Gypsum (CaSO₄·2H₂O) is added to cement clinker (about 3-5%) to retard the setting time. Without gypsum, cement would set almost immediately upon adding water (flash set) due to the rapid reaction of tricalcium aluminate. Gypsum allows sufficient time for mixing and placing.
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