Question

# The composition of copper mattel is-[A]$C{{u}_{2}}S+FeS$ [B]$C{{u}_{2}}S+C{{u}_{2}}O$[C]$C{{u}_{2}}S+FeO$[D]$C{{u}_{2}}O+FeS$

Hint: Copper matte is formed during the extraction of copper from its sulphide ores. Copper matte is obtained in the bottom of the furnace and is a mixture of sulphides. It is further purified to obtain pure copper.
Complete step by step solution: During the extraction of copper from its ore, the ore is treated with various processes in order to separate from impurities and obtain pure metal.
We will discuss the extraction of ore from its sulphide ore in order to find out the composition of copper matte-
As we know, copper is generally extracted from its ore copper pyrite ($CuFe{{S}_{2}}$), which is a sulphide ore of copper.
At first the ore is crushed into fine powder and then concentrated by froth floatation.
The concentrated ore is then roasted at high heat in presence of oxygen to remove moisture and other impurities like sulphides and oxides. As a result of roasting, copper pyrite is converted into ferrous sulphide and cuprous sulphide-

$2CuFe{{S}_{2}}+{{O}_{2}}\to C{{u}_{2}}S+2FeS+S{{O}_{2}}$

The roasted ore is mixed with powdered coke and is heated at a very high temperature in a furnace where hot air is blasted in the lower part. This process is referred to as smelting.
As a result of smelting, ferrous sulphide is converted into ferrous oxide which is combined with silica and forms a slug

$FeS+3{{O}_{2}}\to 2FeO+2S{{O}_{2}}$
$FeO+Si{{O}_{2}}\to FeSi{{O}_{3}}$

During roasting, if any if any copper oxide is formed, it combines with FeS and changes back into its sulphide
\begin{align} & 2C{{u}_{2}}S+3{{O}_{2}}\to 2C{{U}_{2}}O+2S{{O}_{2}} \\ & C{{u}_{2}}O+FeS\to C{{u}_{2}}S+FeO \\ \end{align}

Due to smelting, two layers are formed at the bottom of the furnace. The upper layer is the slag as it is lighter and the bottom of the furnace contains a molten mass mostly of cuprous sulphide and some ferrous sulphide. This molten mass is known as copper matte and is further purified to blister copper and electrically refined copper.

Thus, the composition of copper matte is $C{{u}_{2}}S+FeS$.

Therefore, the correct answer is option [A] $C{{u}_{2}}S+FeS$

Note: As we can see that both oxides and sulphides are found in the furnace at the same time but the oxides are converted into slag in presence of silica and the molten matte is settled in the bottom. The sulphides settled at the bottom are called copper matte therefore the answer is the option which has both copper and ferrous sulphide even though it contains some amount of ferrous sulphide.