Question

Which of the following metals can be reduced by carbon reduction as well as self reduction?
A. $Fe$
B. $Al$
C. $Pb$
D. None of these

Answer 1

Hint: We know that sulphide ore of less electropositive metals such as copper, mercury and lead etc. can be reduced to oxide when heated in air, which later on reacts with remaining sulphide ore to give metals. Carbon can be used as a reducing agent for metal oxides as carbon is more active than any transition metals. Aluminum and iron are more electropositive metals than lead hence they do not show properties like lead.Carbon can also reduce lead oxide to lead on heating lead oxide with coke (carbon). Lead is extracted from its ore by carbon reduction method.

Step-By-Step answer:
Self-reduction reaction of lead metal - In the self reduction process of lead sulphide is heated in air then lead sulphide is converted into lead oxide. Lead oxide then reacts with the remaining lead sulphide to give lead metal. Thus self-reduction of lead is performed.
$\begin{gathered} 2PbS + 3{O_2} \to 2PbO + 2S{O_2} \\\ PbS + 2PbO \to 3Pb + S{O_2} \\\ \end{gathered}$
Carbon reduction reaction of lead oxide - Lead oxide can be reduced to lead metal. This reaction is used in the metallurgy of lead metal.
$2PbO + C \to 2Pb + C{O_2}$
Hence only lead metal can be reduced by carbon reduction as well as self-reduction. Here option C is the correct answer to this problem that is $Pb$.

Note : Metals are often found in their ores as sulphides and oxides. Lead sulphide can be converted to oxide by roasting in air. Then it self reduces to metal later in the reaction. The carbon can be added to lead oxide and heated to reduce lead metal. Carbon can extract any metal which is placed below in the reactivity series. Using carbon for reduction or extraction of metals is a relatively very cheap way. Carbon is used in the form of coke.