The bleaching action of bleaching powder is due to: MCQ with Answer and Explanation

The bleaching action of bleaching powder is due to:
A. Chlorine liberated in the presence of acid
B. Sodium hypochlorite
C. Hydrogen peroxide
D. Ozone
Answer: Option A
Solution (By JKSSB Mock Tests)
Bleaching powder (CaOCl₂) reacts with dilute acids or even CO₂ from air to release chlorine: CaOCl₂ + H₂SO₄ → CaSO₄ + Cl₂ + H₂O; or with CO₂: CaOCl₂ + CO₂ → CaCO₃ + Cl₂. The chlorine gas acts as oxidizing and bleaching agent. Actually the bleaching is due to nascent oxygen produced by chlorine with water: Cl₂ + H₂O → 2HCl + [O]. But the key is chlorine liberation.

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Question #1
Brass is an alloy of:
A. Copper and zinc
B. Iron and carbon
C. Copper and tin
D. Aluminium and copper

Correct Answer: Option A


Explanation:
Brass: Cu + Zn. Bronze: Cu + Sn. Steel: Fe + C. Duralumin: Al + Cu + Mg + Mn. Brass is corrosion-resistant and used in plumbing, musical instruments. Zinc content varies (5-45%). Brass with higher zinc is stronger but less ductile. Some brasses contain small amounts of other elements.

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Question #2
The geometry and magnetic nature of the [Ni(CN)4]2- complex is:
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B. Tetrahedral, diamagnetic
C. Square planar, diamagnetic
D. Square planar, paramagnetic

Correct Answer: Option C


Explanation:
In [Ni(CN)4]2-, Ni is in the +2 oxidation state (d8 configuration). CN- is a strong field ligand, causing the pairing of d-electrons. This leaves one empty d-orbital, leading to dsp2 hybridization. The geometry is square planar. Since all electrons are paired, the complex is diamagnetic.

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The element with the highest electronegativity in the periodic table is:
A. Fluorine
B. Nitrogen
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D. Chlorine

Correct Answer: Option A


Explanation:
Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond. It increases across a period and decreases down a group. Fluorine, located at the top right of the periodic table (Group 17, Period 2), has the smallest atomic radius and highest effective nuclear charge, giving it the highest electronegativity (3.98 on Pauling scale).

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