When conc. H_2SO_4 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). (a) Identify the gases (A) and (B). (b) Write the equations for the reactions involved.

When conc. H_2SO_4 was added into an unknown salt present in a test tu

1.	When conc. H_2SO_4 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). (a) Identify the gases (A) and (B). (b) Write the equations for the reactions involved.
Answer» Solution :(a) GAS (A) - `NO_2 ` ( BROWN gas ) Gas (B) - `N_2O_4` ( colourless gas ). (b) `MNO_3 + H_2SO_4 to MHSO_4 + HNO_4` `Cu + HNO_3 to Cu(NO_3)_2 + 2H_2O + underset("Brown gas ")(2NO_2)` `underset((A))(2NO_2) OVERSET(" On COOLING ")to underset("(B) colourless ")(N_2O_4)`