Question

Upon heating with $C{u_2}S$, the reagent(s) that give copper metal is/are :
a.) $CuFe{S_2}$
b.) CuO
c.) $C{u_2}O$
d.) $CuS{O_4}$

Answer 1

Hint: The answer to this are the reagents that can reduce copper sulphide. Because the metallic copper is formed from reduction of copper sulphide along with sulphur dioxide. So, the reagents from above that can reduce $C{u_2}S$ will be the favourable ones.

Complete step by step answer:
For this, we need to see the reaction of all the reagents with the $C{u_2}S$ on heating. The comparison of products will help us in finding our answer.
So, the first reagent given is $CuFe{S_2}$. This reagent upon heating with oxygen gives $C{u_2}S$ along with two molecules of FeS and sulphur dioxide. The reaction is written as -
$2CuFe{S_2} + {O_2}\xrightarrow{\Delta }C{u_2}S + 2FeS + S{O_2}$

So, this reagent does not give copper metal. Thus, this is not the correct answer.
The next reagent given is CuO. This CuO on heating produces $C{u_2}O$. This $C{u_2}O$ reacts with $C{u_2}S$ to yield metallic copper. The reaction is -
$4Cu\xrightarrow{{{{1100}^0}C}}2C{u_2}O + {O_2}$
$2C{u_2}O + C{u_2}S\xrightarrow{\Delta }6Cu + S{O_2}$

So, this can be the correct answer. Thus, the option b.) is the correct answer.
The third reagent is $C{u_2}O$. The $C{u_2}O$ reacts with $C{u_2}S$ to yield metallic copper. The reaction is -
$2C{u_2}O + C{u_2}S\xrightarrow{\Delta }6Cu + S{O_2}$
So, this can be the correct answer. Thus, the option c.) is the correct answer.

The fourth reagent is $CuS{O_4}$. This $CuS{O_4}$ on heating produces CuO which on further heating gives $C{u_2}O$. This $C{u_2}O$ reacts with$C{u_2}S$ to yield metallic copper. The reaction is -
$CuS{O_4}\xrightarrow{{{{720}^0}C}}CuO + S{O_2} + \dfrac{1}{2}{O_2}$
$4Cu\xrightarrow{{{{1100}^0}C}}2C{u_2}O + {O_2}$
$2C{u_2}O + C{u_2}S\xrightarrow{\Delta }6Cu + S{O_2}$

So, even this can be the correct answer. Thus, the option c.) is the correct answer.
So, the correct answer is “Option B, C and D”.

Note: The above reactions are thought to proceed via following mechanism.
$C{u_2}S \rightleftarrows 2C{u^ + } + {S^{2 - }}$
$2C{u_2}O \rightleftarrows 4C{u^ + } + 2{O^{2 - }}$
${S^{2 - }} + 2{O^{2 - }} \to S{O_2} + 6{e^ - }$
$6Cu + 6{e^ - } \to 6Cu$
The copper sulphide is reduced here to metallic copper with evolution of sulphur dioxide gas.