Which one of the following reactions is not possible?

Which of the following is a true statement?

Iodine is released when potassium iodide reacts with

When $KMnO_4$ solution is titrated with a solution containing $Fe^{2+}$ ions,the indicator used in this titration is

The treatment of an aqueous solution of $3.74 \ g$ of $Cu(NO_3)_2$ with excess $KI$ results in a brown solution along with the formation of a precipitate. Passing $H_2S$ through this brown solution gives another precipitate $X$. The amount of $X$ (in $g$) is. . . . . [Given : Atomic mass of $H=1, N=14, O=16, S=32, K=39, Cu=63, I=127$ ]

Which gases are formed by the oxidation of carbon with concentrated $H_2SO_4$?