In the electrolytic reduction of alumina,why is cryolite $(Na_3AlF_6)$ primarily added?

In the extraction of metals from sulphide ores,the ore is first converted into an oxide before reduction,rather than reducing the sulphide ore directly,because .....

Given below are two statements.
Statement $I$: According to the Ellingham diagram,any metal oxide with higher $\Delta G^{\circ}$ is more stable than the one with lower $\Delta G^{\circ}$.
Statement $II$: The metal involved in the formation of oxide placed lower in the Ellingham diagram can reduce the oxide of a metal placed higher in the diagram.
In the light of the above statements,choose the correct answer from the options given below.

Describe the process of obtaining blister copper.

Extraction of gold $(Au)$ involves the formation of complex ions $X$ and $Y$ as shown in the reaction: $\text{Gold ore}$ $\xrightarrow{CN^-, H_2O, O_2} HO^- + X$ $\xrightarrow{Zn} Y + Au$. $X$ and $Y$ respectively are:

The cyanide process of gold extraction involves leaching out gold from its ore with $CN^{-}$ in the presence of $Q$ in water to form $R$. Subsequently,$R$ is treated with $T$ to obtain $Au$ and $Z$. Choose the correct option$(s)$.
$1$. $T$ is $Zn$
$2$. $R$ is $[Au(CN)_2]^-$
$3$. $Z$ is $[Zn(CN)_4]^{2-}$
$4$. $Q$ is $O_2$