Question

Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time, the passage of air is stopped, but the heating is continued in a closed furnace such that the contents undergo self-reduction. The weight (in kg) of $Pb$ produced per kg of ${O_2}$ consumed is ……
[Atomic weight in $gmo{l^{ - 1}}:O = 16,S = 32,Pb = 207]$

Answer 1

Here in this question, Galena(an ore) undergo in self-reduction process which means the cations of the less electropositive metals like $Pb,Hg,Sb\;{\text{and Cu}}$ may be reduced without the use of any additional reducing agent and the gram per moles is the mass of a substance in grams but numerically equal to its nuclear weight. It is also called gram-molecular weight. If we see, take an example like a gram per mole of oxygen is 16g, and $Pb$ is 207 g.

Complete step by step answer:
From our given data and conditions, as we need to calculate the weight of $Pb$ produced per kg of ${O_2}$ .
In the reaction it is involved in the extraction of $Pb$ from galena.
$PbS + {O_2} \to Pb + S{O_2}$,
Therefore, use of 1 kg of ${O_2}$means 1000g of ${O_2}$ is used there.
Moles of ${O_2}$= $\dfrac{{100}}{{Molecular\;{\text{mass}}}}g.$
In this, molecular mass of ${O_2} = 32$

Moles of ${O_2} = \dfrac{{1000}}{{32}}g$
So, According to stoichiometry,
No of moles of ${O_2}$= No. of moles of Pb
Which is equal to $\dfrac{{100}}{{32}}g$
Then, Mass of Pb =No. of moles of Pb $\times$ molecular mass of Pb.
Mass of Pb $\dfrac{{1000}}{{32}} \times 207g\; \Rightarrow {\text{6470g}}$
Further we have to convert 6470 into Kg. where 1 Kg.=1000g.
$6470g = \dfrac{{6470}}{{1000}}kg$
Mass of Pb=6.47kg.
Additional information: Here is an interesting information, Galena is the world primary ore of lead. It is a lead sulphide mineral with a chemical composition of Pbs. Galena is also called lead glance, a grey lead sulphide Pbs. It is often mined as a source of silver as well as lead and the molecular weight is also known as the molecular mass. This is almost the same as the atomic weight. So, let us take an example, the atomic weight is equal to the molecular mass of oxygen which is 16g and for Pb(lead) is 207g.

Note:
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals.