Question

the oxides of metals like hg can be reduced by heating only

Answer 1

The oxides of metals like mercury can be reduced by heating only in air.
     2HgS + 3O2 =  HgO + 2SO2
     2HgO = 2Hg + O2

Answer 2

Hello there,

● Explanation -
- Mercury is at the bottom of reactivity series. i.e. less reactive.
- Oxide of less reactive metals can be reduced by simple heating. They don't need any other metal for reduction.
- Hence, mercury can be reduced by heating only.
2HgO(s) + ∆ --> 2Hg(l) + O2(g)

Hope this solved your doubts.
Thanks for asking...