Which of the following will not change the orange colour of $K_2Cr_2O_7$ into green colour in an acidic medium?

Which of the following species is both basic and a reducing agent?

$H_2S$ ($5$ moles) reacts completely with acidified aqueous potassium permanganate solution. In this reaction,the number of moles of water produced is $x$,and the number of moles of electrons involved is $y$. The value of $(x+y)$ is. . . . . .

$6 \times 10^{-3} \text{ mole}$ of $K_2Cr_2O_7$ reacts completely with $9 \times 10^{-3} \text{ mole}$ of $X^{n+}$ to give $XO_3^-$ and $Cr^{3+}$. The value of $n$ is:

Which of the following ions decolorizes acidic $KMnO_4$ solution?

$15 \ mL$ of aqueous solution of $Fe^{2+}$ in acidic medium completely reacted with $20 \ mL$ of $0.03 \ M$ aqueous $Cr_{2}O_{7}^{2-}$. The molarity of the $Fe^{2+}$ solution is ........... $\times 10^{-2} \ M$ (Round off to the Nearest Integer).