Q1 · CSIR-NET Chemistry, December 2019

Paper: CSIR-NET December 2019 · Subject: Inorganic Chemistry · Chapter: Acids and Bases · Topic: Acid and Bases – General · Marks: 2 · Difficulty: Easy

Under review — part of this question (a structure or an option) is not clear in the source scan. 4AB is checking it against the original book; the answer shown may change.
Choose the equilibria from the following that are NOT favoured to go to right
\[ \begin{array}{l} \text{(A) } \mathrm{As_2S_5} + 5\mathrm{HgO} \xleftrightarrow{\text{gives}} \mathrm{As_2O_5} + 5\,\mathrm{HgS} \\ \text{(B) } \mathrm{La_2(CO_3)_3} + \mathrm{Bi_2S_3} \xleftrightarrow{\text{gives}} \mathrm{La_2S_3} + \mathrm{Bi_2(CO_3)_3} \\ \text{(C) } \mathrm{CaSO_4} + \mathrm{CaS} \xleftrightarrow{\text{gives}} \mathrm{CdS} + \mathrm{CaSO_4} \\ \text{(D) } \mathrm{BeF_2} + \mathrm{HgI_2} \xleftrightarrow{\text{gives}} \mathrm{BeI_2} + \mathrm{HgF_2} \end{array} \]
(a)A and B
(b)A and C
(c)B and C
(d)B and D
Answer
Under review — not yet confirmed.
Answer: D
Explanation
HSAB: hard acids prefer hard bases. (A) As(V)–O and Hg–S are the matched pairs, so it goes right. (B) La³⁺ (hard) with S²⁻ and Bi³⁺ (soft) with CO₃²⁻ is the mismatched side, so it does not go right. (C) Cd²⁺ (soft) with S²⁻ and Ca²⁺ (hard) with SO₄²⁻ go right. (D) Be²⁺ (hard) with I⁻ and Hg²⁺ (soft) with F⁻ is mismatched, so it does not go right. Not favoured: B and D.

Study loop for Acids and Bases

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