Single Choice

Zinc oxide is normally white but turns yellow on heating and becomes white again on cooling because of:

Ad - d transition spectra as well as a crystal defect
Bthe two-dimensional netweork structure of ZnO
Cits high transition temperature $$(T_{C})$$
Dvarious types of lattice defects because of which the oxygen ion is lost during heating
Correct Answer

Solution

$$ZnO$$ is an example of non-stoichiometric defect under the category of metal excess defect (excess cations occupy interstitial site). In $$ZnO$$, $$Zn^{2+}$$ occupy at interstitial sites and hence, electrons are trapped at interstitial sites for neutralization. Crystals showing such type of defects are generally colored. Zinc oxide is usually white in color but turns yellow on heating because it loses oxygen reversibly at high temperatures. $$ZnO \rightarrow Zn^{2+}+\dfrac{1}{2}O_{2}+2e^-$$

SIMILAR QUESTIONS

d - block and f - block Elements

Which of the following is an amphoteric oxide?

d - block and f - block Elements

Which of the following compound is blue?

d - block and f - block Elements

Which of the following oxides are basic in nature ?

d - block and f - block Elements

The Oxidation states of $$Cr$$ in $$[Cr(H_2O)_6]Cl_3, [Cr(C_6H_6)_2]$$, and $$K_2[Cr(CN)_2(O)_2(O_2)(NH_3]$$ respectively are:

d - block and f - block Elements

Which of the following compounds is metallic and ferromagnetic?

d - block and f - block Elements

In acidic medium, $$H_2O_2$$ changes $$Cr_2O_7^{- 2}$$ to $$CrO_5$$ which has two ($$-O- O-$$) bonds oxidation state of $$Cr$$ in $$CrO_5$$ is:

d - block and f - block Elements

Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

d - block and f - block Elements

$$Cr - C$$ bond in the compound $$[Cr(CO)_6]$$ shows $$\pi$$ - character due to :

d - block and f - block Elements

Passivity of iron is due to formation of:

d - block and f - block Elements

Fe is made passive by:

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