Assign $A, B, C, D$ from the given type of reaction.
$2F_2 + 2H_2O \longrightarrow 4HF + O_2$

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?

Which of the following is not a redox reaction?

$(NH_4)_2Cr_2O_7$ (Ammonium dichromate) is used in fireworks. The green coloured powder blown in air is

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 one of the following reactions does not take place?