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The p-Block Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryThe p-Block Elements5 Marks
Question
Answer the following question:
When conc. H2SO4 was added into an unknown salt present in a test tube, a brown gas (A) was evolved. This gas intensified when copper turnings were also added into this test tube. On cooling, the gas (A) changed into a colourless gas (B).
  1. Identify the gases A and B.
  2. Write the equations for the reactions involved.
✓

Answer

$\text{A}=\text{NO}_2\text{(g)}, \ \text{B}= \text{N}_2\text{O}_4\text{(g)}$
$\text{MNO}_3+\text{H}_2\text{SO}_4\ \ \ \xrightarrow{\ \ \text{Heat}\ \ \ }\ \ \ \text{MHSO}_4+\text{HNO}_3$
$4\text{HNO}_3 \ \ \ \ \ \xrightarrow{\ \ \text{Heat}\ \ \ }\ \ \ \ \ \ \ \ 4\text{NO}_2\ \ \ \ +\ \ \ \ 2\text{H}_2\text{O}\ \ \ + \ \ \text{O}_2\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ^\text{Nitrogen dioxide}\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ^\text{(Brown gas)}$
$\ \ \ \ \ \ \ \ \text{Cu}\ \ \ +\ \ \ 4\text{HNO}_3 \ \ \xrightarrow{\ \ \text{Heat}\ \ \ }\ \ \text{Cu(NO}_3)_2\ +\ 2\text{H}_2\text{O}\ 2\ +\ \text{NO}_2\\^\text{Copper turnings}$

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