Metal Excess Defect

Q.

Explain Schottky and Frenkel defects.

Q.

What is the metal excess defect? Explain with examples.

Q.

A solution of [Ni(H₂O)₆]²⁺ is green but a solution of [Ni(CN)₄]²⁻ is colourless. Explain.

Q.

Explain Schottky defect and Frenkel defect.

Q.

When metal ‘M’ is treated with NaOH, a white gelatinous precipitate ‘X’ is obtained, which is soluble in excess of NaOH. Compound ‘X’ when heated strongly gives an oxide which is used in chromatography as an adsorbent. The metal ‘M’ is

1. $\mathrm{Ca}$

2. $\mathrm{Al}$

3. $\mathrm{Fe}$

4. $\mathrm{Zn}$

Q. When an extra cation and electron occupies the interstitital sites in its crystal lattice, it is called:

1. Schottky defect
2. Frenkel defect
3. Metal excess defect
4. Stoichiometric defect

Q.

Why does table salt, NaCl sometimes appear yellow in colour?

Q.

[Fe(CN)₆]⁴⁻ and [Fe(H₂O)₆]²⁺ are of different colours in dilute solutions. Why?

Q.

Why does silver bromide (AgBr) show both Schottky and Frenkel defects? ( in simple words)

Q. Which of the following defect produces F-centres ?

1. Metal excess defect
2. Scottky defect
3. Metal deficiency defect
4. Vacancy defect

Q. If a electron is present in place of anion in a crystal lattice, then it is called

1. Frenkel defect
2. Schottky defect
3. Interstitial defect
4. F-centre

Q.

Those elements impart colour to the flame on heating in it, the atoms of which require the low energy of the ionization (i.e., absorb energy in group visible region of the spectrum). The elements of which of the following groups will impart colour to the flame?
(a) 2 (b) 13 (c) 1 (d) 17

Q.

The red color of ruby is due to __________

Q.

How Metal excess defect is caused by the presence of extra cations in the interstitial sites?

Q.

In metal excess defect, anions all missed from their lattice sites and they are occupied by electrons to maintain electrical neutrality. These sites occupied by electrons are called F-centers.

What is the effect of metal excess defect on density of the crystal?

1. Does Not have any effect

2. Increases

3. Decreases

4. Decreases, then increases

Q. If an electron is present in place of anion in a crystal lattice, then it is called

1. Frenkel defect
2. Schottky defect
3. Interstitial defects
4. F-centre

Q. Schottky defects are observed in solids with cations and anions of similar sizes. Which of the following compounds, therefore, is NOT likely to have a Schottky defect?

1. NaCl
2. AgCl
3. CsCl
4. KCl

Q.

Why does white ZnO (s) becomes yellow upon heating ?

Q.

An excess of potassium ions makes KCL crystals appear violet or lilac colour since ................

(a) some of the anionic sites are occupied by an unpaired electron

(b) some of the anionic sites are occupied by a pair of electrons

(c) there are vacancies at some anionic sites

(d) F-centres are created which impart colors to the crystals

Q. Assertion: Anion vacancies in alkali halides are produced by heating the alkali halide crystals with alkali metal vapour.
Reason: Electrons trapped in anion vacancies are referred to as F-centers.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If assertion is true but reason is false.
3. If the assertion and reason both are false.
4. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Q.

Paragraph :In metal excess defect, anions all missed from their lattice sites and they are occupied by electrons to maintain electrical neutrality. These sites occupied by electrons are called F-centers.

Question: The colour of NaCl changes when heated in sodium vapour due to

1. Excess of sodium in the crystal

2. Electrons in the voids

3. Excess of chlorine in the crystal

4. Deficiency of sodium in the crystal

Q. Cementite is:

1. Interstitial compound of iron and carbon
2. An alloy of $Fe$ and $Cr$
3. A compound resembling cement
4. An ore of iron

Q.

What is f centre give some example also

Q. If $H{g}_{2}C{l}_2$ is 80% ionised in the aqueous solution what will be the van't Hoff factor of $H{g}_{2}C{l}_2$ in the solution?

1. 1.6
2. 2.6
3. 3.6
4. 4.6

Q. Which of the following statements regarding defects in solids is/are correct?

1. Frenkel defect is usually favoured by a very small difference in the sizes of cation and anion.
2. Frenkel defect is a dislocation defect.
3. Trapping of an electron in the lattice leads to the formation of F-center.
4. Schottky defects have no effect on the physical properties of solids.

Q.

1. Metal excess defect
2. Frenkel defect
3. Schottky defect
4. None of the above

Q.

Paragraph :In metal excess defect, anions all missed from their lattice sites and they are occupied by electrons to maintain electrical neutrality. These sites occupied by electrons are called F-centers.

Question: In metal excess defect

1. anions miss from their lattice points

2. Cations miss from their lattice points

3. Both cations and anions miss from their lattice points

4. Extra anions are doped

Q. Which of the following defect produces F-centres ?

1. Metal excess defect
2. Scottky defect
3. Metal deficiency defect
4. Vacancy defect

Q. $H_{2}S$ gas when passed through a solution of cations containing $HCl$ precipitates the cations of the second group of qualitative analysis but not those belonging to the fourth group. It is because:

1. Presence of $HCl$ decreases the sulphide ion concentration.
2. Sulphides of group IV cations are unstable in $HCl$
3. The solubility product of group II sulphides is more than that of group IV sulphides
4. Presence of $HCl$ increases the sulphides ion concentration

Q.

The name for hydrogen comes from words meaning

1. Water-fearing

2. Water forming

3. Fire forming

4. Gas