Question

Which of the following statement is correct when a mixture of $NaCl$ and $K_{2}Cr_{2}O_{7}$ is gently warmed with $conc.H_{2}SO_{4}$ ?
$1$ . A deep red vapour is evolved
$2.$ The vapour when passed into $NaOH$ solution gives a yellow solution of $Na_{2}CrO_{4}$
$3.$ Chlorine gas is evolved
$4.$ Chromyl chloride is formed

• A. 1, 2, 4
• B. 1, 2 ,3
• C. 2, 3, 4
• D. all are correct

Answer 1

Answer: (A)

$4NaCl+K_{2}\left(Cr\right)_{2}O_{7}+6H_{2}\left(SO\right)_{4}\left(conc .\right) \rightarrow 2\left(KHSO\right)_{4}+4\left(NaHSO\right)_{4}+\underset{\underset{Chromyl chloride}{\left(orange red\right)}}{2 \left(CrO\right)_{2} \left(Cl\right)_{2}}+3H_{2}O$
Chromyl chloride vapours when passed through $NaOH$ solution gives a yellow solution of $Na_{2}CrO_{4}$ .
$CrO_{2}Cl_{2}+4NaOH \rightarrow Na_{2}CrO_{4}+2NaCl+2H_{2}O$