Question

What is the color of zinc oxide when it is hot and when it is cold is
A.White, yellow
B.Yellow, white
C.White, green
D.Yellow, green

Answer 1

Hint:We know that zinc oxide is an amphoteric oxide. It reacts with acid to yield salts of zinc, and with strong alkalis to produce zincates. It assumes yellow color when heated strongly, but that disappears on cooling.

Complete step by step answer:
We know that zinc oxide is amphoteric (reacts with acids and base) and has chemical formula \[ZnO.\] it appears as white powder and is insoluble in water. It is found in earth crust as zincite.
We can use zinc oxide to treat inflammations of skins where it acts as disinfectant ointments. Zinc oxide can also be used in semiconductors, ceramic, concrete, glass compositions and cigarette filters.
We know that in pure state, zinc oxide appears as white oxide. In nature, it occurs as ore zincite that comprises manganese and other impurities, which gives yellow to red color to zinc oxide.
Zinc oxide in its crystalline state is thermo-chromic, turns from white to yellow when heated and on cooling it turns white.
On heating above ${800^ \circ }C,$ zinc oxide turns yellow but on cooling it reverts to white. The zinc oxide in hot state absorbs few of the blue wavelengths of light and the reflected light is yellow.

Hence option (A) is correct.

Note:
We can use zinc oxide for various applications. Such as
-Usage in rubber industry
-Vulcanization of rubber along stearic acid to yield tires, shoe soles pucks of hockey
-Manufacture of concrete
-Addition of zinc oxide enhances resistance to water in processing concrete
-Antibacterial and deodorizing properties