The Solid State - Revision Session - NEET & AIIMS 2019Contact Number: 9667591930 / 8527521718

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Triclinic crystal has the following unit cell parameters:

1. a = b = c; $\mathrm{\alpha}$ = $\mathrm{\beta}$ = $\mathrm{\gamma}$ = 90°

2. a = b $\ne $ c; $\mathrm{\alpha}$ = $\mathrm{\beta}$ = $\mathrm{\gamma}$ = 90°

3. a $\ne $ b $\ne $ c; $\mathrm{\alpha}$ $\ne $ $\mathrm{\beta}$ $\ne $ $\mathrm{\gamma}$ $\ne $ 90°

4. a = b $\ne $ c; $\mathrm{\alpha}$ = $\mathrm{\beta}$ = 90°, $\mathrm{\gamma}$ = 120°

Which of the crystal contains the maximum number of Bravais lattices?

1. Cubic

2. Hexagonal

3. Triclinic

4. Orthorhombic

The crystal system of a compound with unit cell parameters, a = 0.328 nm, b = 0.328 nm, c = 0.527 nm and $\mathrm{\alpha}=\mathrm{\beta}=\mathrm{\gamma}$ = 90° is:

1. Cubic

2. Tetragonal

3. Monoclinic

4. Rhombohedral

An element X (At. Wt = 80 g/mol) having fcc structure, calculate no. of unit cells in 8 gm of X:

1. 0.4 X ${\mathrm{N}}_{\mathrm{A}}$

2. 0.1 X ${\mathrm{N}}_{\mathrm{A}}$

3. 4 X ${\mathrm{N}}_{\mathrm{A}}$

4. None of these

Molybdenum (At. Wt. = 96 g ${\mathrm{mol}}^{-1}$) crystallizes as bcc crystal. If density of crystal is 10.3 g/${\mathrm{cm}}^{3}$, then the radius of Mo atom is (use ${\mathrm{N}}_{\mathrm{A}}$ = 6x ${10}^{23}$):

1. 111 pm

2. 314 pm

3. 135.96 pm

4. None of these

The atomic radius of strontium (Sr) is 215 pm and it crystallizes with a cubic closest packing. The edge length of the cube is:

1. 430 pm

2. 608.2 pm

3. 496.53 pm

4. None of these

In the spinel structure, oxide ions are cubical-closest packed whereas 1/8th of tetrahedral voids are occupied by ${\mathrm{A}}^{2+}$ cation, and 1/2 of octahedral voids are occupied by ${\mathrm{B}}^{3+}$ cations. The general formula of the compound having a spinel structure is:

1. ${\mathrm{A}}_{2}{\mathrm{B}}_{2}{\mathrm{O}}_{4}$

2. ${\mathrm{AB}}_{2}{\mathrm{O}}_{4}$

3. ${\mathrm{A}}_{2}{\mathrm{B}}_{4}{\mathrm{O}}_{2}$

4. ${\mathrm{A}}_{4}{\mathrm{B}}_{2}{\mathrm{O}}_{2}$

An alloy of copper, silver, and gold is found to have copper constituting the ccp lattice. If silver atoms occupy the edge centers and gold is present at body center, the alloy will have the formula:

1. ${\mathrm{Cu}}_{4}{\mathrm{Ag}}_{2}\mathrm{Au}$

2. ${\mathrm{Cu}}_{4}{\mathrm{Ag}}_{4}\mathrm{Au}$

3. ${\mathrm{Cu}}_{4}{\mathrm{Ag}}_{3}\mathrm{Au}$

4. CuAgAu

A binary solid (AB) has a rock salt structure. If the edge length is 400 pm, and radius of cation is 80 pm the radius of anion is:

1. 100 pm

2. 120 pm

3. 250 pm

4. 325 pm

An ionic compound AB has fluorite type structures. If the radius ${\mathrm{B}}^{-}$ is 200 pm, then the ideal radius of ${\mathrm{A}}^{+}$ would be:

1. 82.8 pm

2. 146.4 pm

3. 40 pm

4. 45 pm

Which of the following statements for crystals having Schottky defect is not correct?

1. The Schottky defect arises due to the absence of a cation and anion from the position which it is expected to occupy

2. The Schottky defect is more common in ionic compounds with high coordination numbers

3. The density of the crystals having Schottky defect is larger than that of the perfect crystal

4. The crystal having Schottky defect is an electrical defect is electrically neutral as a whole

Which of the following defects does the KBr show?

1. Frenkel

2. Schottky

3. Metal excess

4. Metal deficiency

Dopping of AgCl crystals with ${\mathrm{CdCl}}_{2}$ results in:

1. Schottky defect

2. Frenkel defect

3. Substitutional cation vacancy

4. Formation of F-centres

Select the incorrect statement:

1. stoichiometry of crystal remains unaffected due to Schottky defect

2. Frenkel defect is usually shown by ionic compounds having a low coordination number

3. F-centres generation is the responsible factor for imparting the colour to the crystal

4. Density of crystal always increases due to substitutional impurity defect

When NaCl is dopped with ${10}^{-5}$ mole % of ${\mathrm{SrCl}}_{2}$, what is the no. of cationic vacancies?

1. ${10}^{-5}$ x ${\mathrm{N}}_{\mathrm{A}}$

2. ${10}^{-7}$ x ${\mathrm{N}}_{\mathrm{A}}$

3. 2 x ${10}^{-7}$ ${\mathrm{N}}_{\mathrm{A}}$

4. None of these

The composition of a sample of Wusitite is ${\mathrm{Fe}}_{0.93}\mathrm{O}$. What is the percentage of the iron present as ${\mathrm{Fe}}^{3+}$ in total iron?

1. 15.05%

2. 25%

3. 35%

4. 45%

A crystal lead (II) sulfide has a NaCl structure. In this crystal, the shortest distance between a ${\mathrm{Pb}}^{2+}$ ion and ${\mathrm{S}}^{2-}$ ion is 297 pm. What is the volume of the unit cell in lead sulfide?

1. 209.6 x ${10}^{-24}$ ${\mathrm{cm}}^{3}$

2. 207.8x ${10}^{-23}$ ${\mathrm{cm}}^{3}$

3. 22.3x ${10}^{-23}$ ${\mathrm{cm}}^{3}$

4. 209.8x ${10}^{-23}$ ${\mathrm{cm}}^{3}$

KCl crystallizes in the same type of lattice as does NaCl. Given that ${{\mathrm{r}}_{\mathrm{Na}}}^{+}/{{\mathrm{r}}_{\mathrm{cl}}}^{-}$ = 0.50 and ${{\mathrm{r}}_{\mathrm{Na}}}^{+}/{{\mathrm{r}}_{\mathrm{k}}}^{+}$ = 0.70, calculate the ratio of the side of the unit cell for KCI to that for Nacl:

1. 1.143

2. 1.224

3. 1.414

4. 0.875

An element X (atomic weight = 24 gm/mol) forms a face-centered cubic lattice. If the edge length of the lattice is 4 x ${10}^{-8}$ cm and the observed density is 2.40 x ${10}^{3}$ kg/${\mathrm{m}}^{3}$, then the percentage occupancy of lattice points by element X is : (Use ${\mathrm{N}}_{\mathrm{A}}$ = 6 x ${10}^{23}$):

1. 96

2. 98

3. 99.9

4. None of these

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