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CBSE Class 10 Science 2023 Outside Delhi Set 2

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Question : 7 of 12
Marks: +1, -0
A metal nitrate 'A' on heating gives a metal oxide along with evolution of a brown coloured gas ' BB ' and a colourless gas, which helps in burning. Aqueous solution of ' AA ' when reacted with potassium iodide forms a yellow precipitate.
(a) Identify ' AA ' and ' BB '
(b) Name the types of the reactions involved in the above statement .
Solution:  
The metal in compound AA is lead (Pb)(\mathrm{Pb}). Therefore, we can write
Reaction 1 as:
2Pb(NO3)2→Δ2PbO+4NO2+O22\mathrm{Pb}(\mathrm{NO}_3)_2 \xrightarrow{\Delta} 2\mathrm{PbO}+4\mathrm{NO}_2+\mathrm{O}_2
Reaction 2:
Pb(NO3)2+2KI→Pbl2+2KNO3\mathrm{Pb}(\mathrm{NO}_3)_2+2\mathrm{KI} \rightarrow \mathrm{Pbl}_2+2\mathrm{KNO}_3
Compound A-Lead nitrate: Pb(NO3)2\mathrm{Pb}(\mathrm{NO}_3)_2
Compound B-Nitrogen dioxide- NO2\mathrm{NO}_2
Reaction 1 is thermal decomposition, whereas, reaction 2 is double decomposition reaction.
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