Question

A metal nitrate A on heating gives a yellowish brown coloured metal oxide along with brown gas B and a colourless gas C. An aqueous solution of A on reaction with potassium iodide forms a yellow precipitate of compound D. Identify A, B, C and D. Also, identify the types of reactions taking place. Metal present in A is used in an alloy which is used for soldering purposes.

Answer 1

Hint: Metal alloy used for soldering contains a combination of tin and metal in compound A. The atomic number of this element is 82. This element is also very widely used in car batteries, pigments, ammunition, cable sheathing, etc.

Complete step by step answer:
Let us write the question in the form of an equation. So, according to the question,
Reaction 1:
Metal nitrate (A) \[\xrightarrow{\Delta }\] Yellowish brown metal oxide + Brown gas (B) + Colorless gas (C).
Reaction 2:
Aqueous solution of A + Potassium iodide \[\to \] Yellow precipitate (D)
The last line of the question gives us a hint about the ‘metal’ in compound ‘A’. Soldering is done by a solder, which is an alloy made up of tin and lead.
Therefore, the metal in compound A is lead (Pb).
Therefore, we can rewrite reaction 1 as –
\[2Pb{{(N{{O}_{3}})}_{2}}\xrightarrow{\Delta }2PbO+4N{{O}_{2}}+{{O}_{2}}\]
We can also rewrite reaction 2 as –
\[Pb{{(N{{O}_{3}})}_{2}}+2KI\to Pb{{I}_{2}}+2KN{{O}_{3}}\]
From here, we can see that the lead nitrate on heating gives a yellowish-brown lead oxide along with nitrogen dioxide and oxygen gas. Also, lead nitrate on reaction with potassium iodide gives lead iodide with potassium nitrate.
Therefore, the answer is –
Compound A – Lead nitrate - \[Pb{{(N{{O}_{3}})}_{2}}\]
Compound B – Nitrogen dioxide - \[N{{O}_{2}}\]
Compound C – Oxygen gas - \[{{O}_{2}}\]
Compound D – Lead iodide - \[Pb{{I}_{2}}\] & potassium nitrate - \[KN{{O}_{3}}\]

Additional Information: In this question, reaction 1 is thermal decomposition, whereas, reaction 2 is double decomposition reaction.

Note: Soldering is a process used to join different types of metals together by melting the solder. Solder is a metal alloy which is usually made up of tin and lead which is melted using a hot iron. Solder made up of tin and lead is corrosion resistant and has good electrical properties.