The salt used in the manufacture of plaster of Paris is:
A. CaSO₄·2H₂O
B. CaOCl₂
C. Na₂SO₄
D. CaCO₃
Answer: Option A
Solution (By JKExamLibrary)
Plaster of Paris is prepared by heating gypsum (CaSO₄·2H₂O) at 373 K, removing part of water of crystallization to form CaSO₄·½H₂O. CaCO₃ is limestone.
Explanation:
Atomic number 15 is phosphorus. Electronic configuration: 2, 8, 5. Number of shells = 3 (Period 3). Valence electrons = 5, so it is in group 15 (10+5) for p-block elements. Group 5 is for d-block. Thus Group 15, Period 3.
Explanation:
Ionic (electrovalent) bond is formed by complete transfer of one or more valence electrons from a metal (low ionization energy) to a non-metal (high electron affinity), resulting in oppositely charged ions held by electrostatic forces. Example: Na → Na⁺ + e⁻; Cl + e⁻ → Cl⁻; Na⁺Cl⁻. Covalent bond involves sharing. Coordinate bond involves donation.
Explanation:
Fluorine is the most electronegative element (Pauling scale 3.98). Electronegativity increases across a period and decreases down a group. Hence F > O > Cl > N.
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