Question

Assertion : A lead nitrate on thermal decomposition gives lead oxide, nitrogen dioxide and oxygen.
Reason : Pb(NO3)2 reacts with KI to form yellow ppt of PbI2 and reaction is double displacement as well as precipitation reaction.

Answer 1

Answer:

Both assertion and reason are correct but given reason is not an explanation of assertion.

Explanation:

• When lead nitrate undergoes the thermal decomposition reaction on heating. It gives one solid and two gases, which are yellow colored lead oxide, nitrogen dioxide gas and oxygen gas.

       2Pb(NO₃)₂    $\longrightarrow$  2PbO  +  4NO₂   +   O₂

• The reaction of lead nitrate with potassium iodide is double displacement reaction. Double displacement reaction is in which two compounds react with each other and by exchanging the ions. They will produce two new compounds is called double displacement reaction. When lead nitrate reacts with KI, there is formation of lead iodide which precipitates, so this reaction is also called precipitation reaction.

         Pb(NO₃)₂ (aq.)    +    2KI (aq.)   $\longrightarrow$   PbI₂(s)     +    2KNO₃  

Answer 2

Answer:

Both assertion and reason are correct statements but the reason is not the correct explanation of the above assertion.

Explanation:

When lead nitrate (Pb(NO3)2) undergoes the process of thermal decomposition, then on heating it gives one solid molecule called lead oxide (PbO) which is yellow coloured and two gas molecules namely nitrogen dioxide (NO2) and oxygen gas (O2).

2Pb(NO3)2(aq) -------> 2PbO(s) + 4NO2(g) + O2(g)

The reaction of lead nitrate (Pb(NO3)2) with the potassium iodide (KI) is a type of double displacement reaction. In double displacement reaction, two compounds react with each other and exchange their ions amd hence produce two new compounds. When lead nitrate (Pb(NO3)2) reacts with potassium iodide (KI) , it leads to the formation of lead iodide (PbI2) which precipitates and hence this reaction is called precipitation reaction.

Pb(NO3)2(aq) + KI(aq) --------> PbI2(s) + 2KNO3

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