Which of the following is used to reduce magnetite $(Fe_3O_4)$ to obtain iron?

Extraction of copper by smelting uses silica as an additive to remove

In the extraction of copper from its sulphide ore,the metal is finally obtained by the reduction of cuprous oxide with

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: In the Ellingham diagram,a sharp change in slope of the line is observed for $Mg \rightarrow MgO$ at $\sim 1120^{\circ} C$.
Reason $R$: There is a large change of entropy associated with the change of state.
In the light of the above statements,choose the correct answer from the options given below.

According to the Ellingham diagram,at lower temperatures,the oxidation of $C$ to $CO$ is useful for the reduction of which of the following?

In the extraction of copper,metal is formed in the Bessemer converter due to the reaction: