39) Oxidation number of sulphur in Na₂S₂O₃ is:

40) Equivalent weight of KMnO₄ in alkaline medium is equal to: (M = molar mass)

41) Oxidation numbers of A, B and C are +6, −2 and −1 respectively. What will be the formula of the molecule when A, B and C associate with each other?

42) One mole of X₂H₄ releases 10 moles of electrons to form a compound Y. What should be the oxidation number of X in the compound Y?

43) What should be the oxidation number of S in H₂S₂O₇?