$50 \ cm^{3}$ of $0.04 \ M \ K_{2}Cr_{2}O_{7}$ in acidic medium oxidizes a sample of $H_{2}S$ gas to sulphur. The volume of $0.03 \ M \ KMnO_{4}$ required to oxidize the same amount of $H_{2}S$ gas to sulphur in acidic medium is: (in $cm^{3}$)

Calculate the millimoles of $SeO_3^{2-}$ in solution on the basis of following data: $70 \ mL$ of $\frac{M}{60}$ solution of $KBrO_3$ was added to $SeO_3^{2-}$ solution. The bromine evolved was removed by boiling and excess of $KBrO_3$ was back titrated with $12.5 \ mL$ of $\frac{M}{25}$ solution of $NaAsO_2$. The reactions are given below.
$I. \ SeO_3^{2-} + BrO_3^{-} + H^{+} \to SeO_4^{2-} + Br_2 + H_2O$
$II. \ BrO_3^{-} + AsO_2^{-} + H_2O \to Br^{-} + AsO_4^{3-} + H^{+}$

Which of the following options are correct for the reaction
$2[Au(CN)_2]_{(aq)}^{-} + Zn_{(s)} \rightarrow 2Au_{(s)} + [Zn(CN)_4]_{(aq)}^{2-}$
$A.$ Redox reaction
$B.$ Displacement reaction
$C.$ Decomposition reaction
$D.$ Combination reaction
Choose the correct answer from the options given below:

Which is not the true statement about $KMnO_4$?

Thiosulphate reacts differently with iodine and bromine in the reactions given below:
$2 S_2 O_3^{2-} + I_2 \rightarrow S_4 O_6^{2-} + 2 I^{-}$
$S_2 O_3^{2-} + 4 Br_2 + 5 H_2 O \rightarrow 2 SO_4^{2-} + 8 Br^{-} + 10 H^{+}$
Which of the following statements justifies the above dual behaviour of thiosulphate?

How many moles of $K_2Cr_2O_7$ are reduced by $1$ mole of $Sn^{2+}$?