JEE Advanced 2023 — Paper 1 — CHEM-IV solution

JEE Advanced2023Paper 1CHEM-IV

Match the reactions (in the given stoichiometry of the reactants) in List-I with one of their products given in List-II and choose the correct option.

List-I	List-II
(P) P $_{2}$ O $_{3}$ + 3H $_{2}$ O $\to$	(1) P(O)(OCH $_{3}$ )Cl $_{2}$
(Q) P $_{4}$ + 3NaOH + 3H $_{2}$ O $\to$	(2) H $_{3}$ PO $_{3}$
(R) PCl $_{5}$ + CH $_{3}$ COOH $\to$	(3) PH $_{3}$
(S) H $_{3}$ PO $_{2}$ + 2H $_{2}$ O + 4AgNO $_{3}$ $\to$	(4) POCl $_{3}$
	(5) H $_{3}$ PO $_{4}$

A
P $\to$ 2; Q $\to$ 3; R $\to$ 1; S $\to$ 5
B
P $\to$ 3; Q $\to$ 5; R $\to$ 4; S $\to$ 2
C
P $\to$ 5; Q $\to$ 2; R $\to$ 1; S $\to$ 3
D
P $\to$ 2; Q $\to$ 3; R $\to$ 4; S $\to$ 5

Solution

(P) Hydrolysis of P $_{2}$ O $_{3}$ . Phosphorus trioxide on hydrolysis gives phosphorous acid: $P_{2} O_{3} + 3 H_{2} O \to 2 H_{3} PO_{3}$ . Match $\to$ (2).

(Q) Disproportionation of white phosphorus. P $_{4}$ disproportionates in cold dilute NaOH producing phosphine and sodium hypophosphite: $P_{4} + 3 NaOH + 3 H_{2} O \to 3 NaH_{2} PO_{2} + PH_{3}$ . Match $\to$ (3).

(R) Reaction of PCl $_{5}$ with acetic acid. PCl $_{5}$ converts the carboxylic acid to acetyl chloride, releasing POCl $_{3}$ and HCl: $PCl_{5} + CH_{3} COOH \to CH_{3} COCl + POCl_{3} + HCl$ . Match $\to$ (4).

(S) Oxidation of H $_{3}$ PO $_{2}$ by AgNO $_{3}$ . Hypophosphorous acid is a strong reducing agent; with silver nitrate the phosphorus is oxidised all the way to phosphoric acid while Ag $^{+}$ is reduced to metallic Ag: $H_{3} PO_{2} + 2 H_{2} O + 4 AgNO_{3} \to 4 Ag + 4 HNO_{3} + H_{3} PO_{4}$ . Match $\to$ (5).

Mapping: P $\to$ 2, Q $\to$ 3, R $\to$ 4, S $\to$ 5. Answer: (D).

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