When $KMnO_4$ reacts with acidified $FeSO_4$,which of the following occurs?

$1 \text{ mole of } H_2C_2O_4 \text{ is oxidised by } x \text{ mole of } MnO_4^- \text{ in strong basic medium and } 1 \text{ mole of } NaHC_2O_4 \text{ is oxidised by } y \text{ mole of } MnO_4^- \text{ in acidic medium. Ratio of } x/y \text{ is}$

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

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Pb_3O_4 + 4HNO_3 \rightarrow 2Pb(NO_3)_2 + PbO_2 + 2H_2O$

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

Assign $A, B, C, D$ from the given type of reaction.
$AgNO_3 \,(Solution) + NaF \,(Solution) \longrightarrow$ No reaction