Question

Zno crystal on heating acquires the formula Zn1+xO

Answer 1

on heating, ZnO loses a minute amount of oxygen and there is an excess of Zn²⁺ ions in the crystal

this ques is a 1 marker so this answer is enough I hope

Answer 2

When ZnO crystals are heated to a certain temperature(800°C-900°C) in a open container, its physical appearance changes from white to yellow colour. It should be noted that when it is kept to cool down the white colour comes back.

This phenomena is due to loss of oxygen from the crystal, which is not a chemical change but a non-stoichiometric one, leaving the crystals as Zn(1.00007)O.

1 + x = 1.00007

or, x = 0.00007