Consider the following reactions $\mathrm{A}+\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{CrO}_{2} \mathrm{Cl}_{2}+$ Side Products Little amount $\mathrm{CrO}_{2} \mathrm{Cl}_{2(\text { Vapour })}+\mathrm{NaOH} \rightarrow \mathrm{B}+\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}$ $\mathrm{B}+\mathrm{H}^{+} \rightarrow \mathrm{C}+\mathrm{H}_{2} \mathrm{O}$ The number of terminal ' $O$ ' present in the compound ' C ' is ____.

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · d and f Block Elements

Consider the following reactions

A + NaCl + H_{2} SO_{4} \to CrO_{2} Cl_{2} +

Side Products
Little
amount

CrO_{2} Cl_{2 (Vapour)} + NaOH \to B + NaCl + H_{2} O

B + H^{+} \to C + H_{2} O

The number of terminal '

O

' present in the compound ' C ' is ____.

Answer: 6

The sequence is

K_{2} Cr_{2} O_{7} (A)

reacting with

NaCl

and

H_{2} SO_{4}

to give chromyl chloride

CrO_{2} Cl_{2}

; its vapour with

NaOH

gives sodium chromate

Na_{2} CrO_{4} (B)

; acidification then gives sodium dichromate, whose anion is

Cr_{2} O_{7}^{2 -} (C)

. In the dichromate ion two

CrO_{4}

tetrahedra share a single bridging oxygen, leaving each chromium with three terminal oxygens. The number of terminal oxygen atoms is

6

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Integer answer