A and B formed in the following reactions are: \[ \begin{aligned} & \mathrm{CrO}_{2} \mathrm{Cl}_{2}+4 \mathrm{NaOH} \rightarrow \mathrm{~A}+2 \mathrm{NaCl}+2 \mathrm{H}_{2} \mathrm{O} \\ & \mathrm{~A}+2 \mathrm{HCl}+2 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{~B}+3 \mathrm{H}_{2} \mathrm{O} \end{aligned} \]

(A) $\mathrm{A}=\mathrm{Na}_{2} \mathrm{CrO}_{4}, \mathrm{~B}=\mathrm{CrO}_{5}$

(B) $\mathrm{A}=\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{4}, \mathrm{~B}=\mathrm{CrO}_{4}$

(C) $\mathrm{A}=\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}, \mathrm{~B}=\mathrm{CrO}_{3}$

(D) $\mathrm{A}=\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}, \mathrm{~B}=\mathrm{CrO}_{5}$

JEE Main · 2024 · 30 Jan 2024 · Shift 2 · d and f Block Elements

A and B formed in the following reactions are:

CrO_{2} Cl_{2} + 4 NaOH \to A + 2 NaCl + 2 H_{2} O A + 2 HCl + 2 H_{2} O_{2} \to B + 3 H_{2} O

Answer: (A)

Chromyl chloride reacts with hot aqueous NaOH by hydrolysis and neutralisation to give sodium chromate:

CrO_{2} Cl_{2} + 4 NaOH \to Na_{2} CrO_{4} + 2 NaCl + 2 H_{2} O

; this is A. Acidifying the chromate with HCl in the presence of

H_{2} O_{2}

generates the deep blue peroxochromium species chromium pentoxide,

CrO_{5}

(formally

CrO (O_{2})_{2}

Na_{2} CrO_{4} + 2 HCl + 2 H_{2} O_{2} \to CrO_{5} + 2 NaCl + 3 H_{2} O

; this is B. A is sodium chromate and B is chromium pentoxide,

CrO_{5}

JEE Main · 2024 · 30 Jan 2024 · Shift 2 · Single correct option