Question

A colourless and odourless gas P is evolved during
thermal decomposition of lead nitrate. P reacts with
the main component of biogas to form compounds Q
and R. P, Q and R respectively are
(1) N2O, O2 and H2O (2) CO2, O2 and Cl2
(3) O2, CO2 and H2O (4) O2, CO2 and H2

Answer 1

the first one. ie: N2O,O2 and H20

Answer 2

The correct answer is option (3).

The reaction of thermal decomposition of lead nitrate is shown below -

2Pb(NO3)2 → 2PbO + 4NO2 + O2

So, you can see that the evolved gases are NO2 and O2.

Now, it is said that colorless and odorless gas evolves during the decomposition, so the gas is O2.

Now, O2 reacts with biogas. Biogas is methane, CH4. The reaction is shown below-

CH4 + O2 → CO2 + 2H2O

So, you can see that the compounds Q and R are CO2 and H20.

So, the answer is

P - 02

Q - CO2

R - H20

Therefore, option (3) is the correct answer.