Which of the following is an acidic flux?

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

Which of the following is the mixture used in the thermite process?

Which flux is used to remove $SiO_2$ impurity?

After froth flotation,copper sulfide is reduced by.........

Assertion : Extraction of iron metal from iron oxide ore is carried out by heating with coke.
Reason : The reaction,
$Fe_2O_{3(s)} \to Fe_{(s)} + 3/2 O_{2(g)}$ is a spontaneous process.