Zinc, cadmium and mercury are found in nature as sulphides. Values of standard reduction potentials for the half-reactions are :
M2+(aq)+2e−→M(s)
ME∘Zn−0.76VCd−0.40VHg+0.79V .
Which sulphides give element not oxide on roasting?
Pick the odd word out of the following: lead, arsenic, chlorine, cadmium, mercury, nickel.