Number of moles of $K_2Cr_2O_7$ reduced by one mole of $Sn^{2+}$ ions is

The value of $x$ in the partial redox equation $MnO_4^- + 8H^{+} + xe^- \rightleftharpoons Mn^{2+} + 4H_2O$ is

Assign $A, B, C, D$ from the given type of reaction for the following chemical equation:
$3Fe_{(s)} + 4H_2O_{(g)} \xrightarrow{\Delta} Fe_3O_{4(s)} + 4H_{2(g)}$

In the redox reaction $N_2H_4 + ClO_3^- \to NO + Cl^-$ (in basic medium),how many electrons are added in the reduction half-reaction based on the difference in oxidation states?

In the reaction $Zn + 2H^{+} + 2Cl^{-} \to Zn^{2+} + 2Cl^{-} + H_2$,the spectator ion is

Observe the following stoichiometric equation:
$P_4 + 3 OH^{-} + 3 H_2 O \rightarrow PH_3 + 3 X^{-}$
What is the conjugate acid of $X^{-}$?