When conc. $H_{2} S O_{4}$ was added to an unknown salt present in a test tube , a brown gas A was evolved .The gas intensified when copper turnings were also added into this test tube .On cooling the gas A changed into colourless B. Identify gases A and B.

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

$N_{2} O_{4}, N O_{4}$

$N_{2} O, N O_{2}$

$N O, N O_{2}$

$N O_{2}, N_{2} O_{4}$

answer is A.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

The given salt is a nitrate salt which on reaction with conc. $H_{2} S O_{4}$ gives first vapors of $H N O_{3}$ to give brown gas $(N O_{2})$ .
$\begin{array}{l} 2 N a N O_{3} + H_{2} S O_{4} \overset{H e a t}{\to} N a_{2} S O_{4} + 2 H N O_{3} \\ (C o l o u r l e s s) \end{array}$

$\begin{array}{l} 4 H N O_{3} \overset{H e a t}{\to} 4 N O_{2} + 2 H_{2} O + O_{2} \\ B r o w n g a s \end{array}$

The gas intensified when copper turnings were added due to reduction of $H N O_{3}$ by Cu
$\begin{array}{l} C u + 4 H N O_{3} \overset{H e a t}{\to} C u {(N O_{3})}_{2} + 2 N O_{2} ↑ + 2 H_{2} O \end{array}$
Brown gas(A) on cooling changes into a colorless gas $(B), N_{2} O_{4} . \begin{array}{l} 2 N O_{2} ⇄ N_{2} O_{4} \\ (A) (B) \end{array}$