In which of the following reactions conc. H2SO4 is used as an oxidising reagent?

a.  CaF2 + H2SO4  CaSO4 + 2HFb.  2 HI + H2SO4  I2 + SO2 + 2H2Oc.  Cu + 2H2SO4  CuSO4 + SO2 + 2H2Od.  NaCl + H2SO4  NaHSO4 + HCl

Choose the correct option
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)



Hint: Oxidising agent oxidized other, and itself gets reduced.

In the above given four reactions, (b) and (c) represent oxidizing behaviour of H2SO4 . As we know that oxidizing agent reduces itself as the oxidation state of the central atom decreases. Here, 
2HI-1 + H2S-6O4  I20 + SO2-4 + 2H2O
Cu0 + 2H2SO4+6  Cu+2SO4 + SO2+4 + 2H2O