$KMnO_4$ oxidises oxalic acid in acidic medium. The number of $CO_2$ molecules produced per mole of $KMnO_4$ is

In alkaline medium,the reaction of hydrogen peroxide with potassium permanganate produces a compound in which the oxidation state of $Mn$ is $....$

Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.

Number of moles of $SnCl_2$ required for the reduction of $1$ mole of $K_2Cr_2O_7$ into $Cr^{3+}$ (in acidic medium) is:

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 $X^{-}$?