Explanation

(a)
In Fischer Ringe’s method, air free from moisture and CO_{2} is passed over a heated mixture of $(800℃)$ of 90% CaC_{2} +10% CaCl_{2} in an iron tube , when following reactions take place
CaC_{2}+N_{2} $\overset{800℃}{\rightarrow}$CaCN_{2}+ c
2C+O⟶2CO
C+O_{2} ⟶CO_{2}
2CaC_{2}+3CO_{2} ⟶2 CaCO_{3}+ 5C
CuO+CO⟶Cu+CO_{2}
CO_{2} gas is now absorbed by KOH solution .Thus, a mixture inert gases is obtained.