What's the valency of lead in pbO2

The valence of lead is 4.

Hence the name of the compound is called Lead (IV) oxide.

Given

PbO₂ compound

Required

The valence of Pb

Solution

The oxidation number of element O in the compound = -2, except for OF₂ the oxidation state = + 2 and the peroxides (Na₂O₂, BaO₂) the oxidation state = -1 and superoxide, for example KO₂ = -1/2.

The oxidation state in the uncharged compound = 0,

So The oxidation state of Pb :

Pb + 2.(-2) = 0

Pb - 4 = 0

Pb = +4

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.