Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. Density of iron is 7.87 g cm-3. Use this information to calculate Avogadro's number.

(Atomic mass of Fe = 56.0 u)

1.

2.

3.

4.

Concept Questions :-

Density/Formula/packing fraction/ Semiconductors
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Assertion : An important feature of Fluorite structures is that cations being large in size occupy FCC

lattice points whereas anions occupy all the tetrahedral voids giving the formula unit $A{B}_{2}$(A: cation B: anion).

Reason : There are 6 cations and 12 anions per FCC unit cell of the Fluorite structure.

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

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Assertion : In NaCl crystal each Na ion is touching 6 $C{l}^{‐}$ ions but these $C{l}^{‐}$ ions do not touch each other.

Reason : The radius ratio roe ${r}_{Na}/{r}_{Cl-}$ is greater than 0.414, required for exact fitting.

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

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Assertion : The ratio of and F- per unit cell of ZnS and $Ca{F}_{2}$ is 1:2.

Reason : In ZnS $Z{n}^{2+}$ ions occupy alternate tetrahedral voids and in $Ca{F}_{2}$ F- ions occupy all the tetrahedral voids of FCC unit cell.

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

Concept Questions :-

Density/Formula/packing fraction/ Semiconductors
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Sodium metal crystallizes in bcc lattice with cell edge . The radius of sodium atom will be-

(A) 1.50 $\stackrel{0}{A}$

(B) 1.86  $\stackrel{0}{A}$

(C) 2.80 $\stackrel{0}{A}$

(D) None of these

Concept Questions :-

Density/Formula/packing fraction/ Semiconductors
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The space lattice of graphite is

(A) Cubic

(B) Tetragonal

(C) Rhombic

(D) Hexagonal

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Introduction and Type of Crystal System
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The edge length of cube is 400pm. Its body diagonal would be-

(A) 500 pm

(B) 693 pm

(C) 600 pm

(D) 566pm

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Density/Formula/packing fraction/ Semiconductors
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A metallic element exists as cubic lattice. Each edge of the unit cell is 2.88 $\stackrel{0}{A}$. The density of the metal is 7.20 g $c{m}^{-3}$. How many unit cell will be present in 100 g of the metal -

(A) $6.85×{10}^{2}$

(B) $5.82×{10}^{23}$

(C) $4.37×{10}^{5}$

(D) $2.12×{10}^{6}$

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Density/Formula/packing fraction/ Semiconductors
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Iron crystallizes in a b.c.c. system with a lattice parameter of 2.861 $\stackrel{0}{A}$. Calculate the density of iron in the b.c.c. system (Atomic weight of Fe = 56, ${N}_{A}=6.02×{10}^{23}mo{l}^{-1}$)

(A) 7.92g $m{l}^{-1}$

(B) 8.96g $m{l}^{-1}$

(C) 2.78g $m{l}^{-1}$

(D) 6.72g $m{l}^{-1}$

Concept Questions :-

Density/Formula/packing fraction/ Semiconductors
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An alloy of copper, silver and gold is found to have copper constituting the ccp lattice. If silver atoms occupy the edge centres and gold is present at body centre, the alloy has a formula-

(A) $C{u}_{4}A{g}_{2}Au$

(B) $C{u}_{4}A{g}_{4}Au$

(C) $C{u}_{4}A{g}_{3}Au$

(D) $CuAgAu$

Concept Questions :-

Density/Formula/packing fraction/ Semiconductors