Aluminium metal forms a cubic close-packed crystal structure. Its atomic radius is 125 × 10 - 12 m . Calculate the length of the side of the unit cell.

Cubic closed packing is another name given to face-centred cubic. Hexagonal closed packing and cubic closed packing are one of the forms in which a cubic lattice is arranged and face-centred cubic is one of the types of unit cells. In a cubic close packed structure, the length of the side of unit cell is related to radius by an equation, r = a 2 2 Or a = r × 2 2 Given, atomic radius r = 125 × 10 - 12 m = 125 × 10 - 10 cm = 125 pm . Putting the values in the equation, we get a = 125 × 2 × 1 .414 = 353 .5 pm .

Aluminium metal forms a cubic close-packed crystal structure. Its atomic radius is 125 × 10 - 12 m . How many such unit cells are there in 1 .00 m 3 of aluminium?

Cubic closed packing is another name given to face-centred cubic. Hexagonal closed packing and cubic closed packing are one of the forms in which a cubic lattice is arranged and face-centred cubic is one of the types of unit cells. In a cubic close packed structure, the length of the side of unit cell is related to radius by an equation, a = r × 2 2 Given, atomic radius r = 125 × 10 - 12 m = 125 × 10 - 10 cm = 125 pm . Putting the values in the equation, we get a = 125 × 2 × 1 .414 = 353 .5 pm . Volume of the unit cell = ( a 3 ) = 353.5 × 10 - 10 3 = 4.42 × 10 - 23 cm 3 = 4 . 42 × 10 - 29 m 3 One unit cell contain the volume 4 . 42 × 10 - 29 m 3 Number of unit cells are present in 1 m 3 = ? Number of unit cells in 1 m 3 = 1 4 . 42 × 10 - 29 = 2 .26 × 10 28 unit cells.

ZnO turns yellow on heating. Why?

In ZnO , Zn + 2 ions occupy the interstitial sites and electrons are trapped in the interstitial sites for neutralization. Crystals that show such type of defects are generally coloured. Zinc oxide is white in colour at room temperature. On heating, it loses oxygen and turns yellow.

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IMPORTANT

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$KBr$ has $fcc$ structure. The density of $KBr$ is $2 .75 g {cm}^{- 3}$ . Find the distance between $K^{+}$ and ${Br}^{-}$ . (At mass of $Br = 80 .0$ ).

Important Questions on States of Matter: Solid State

MEDIUM

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 17

Calculate the Avogadro's number from the following data of

AB

when

AB

has

NaCl

type structure : Density of

AB = 2 .48 g {cm}^{- 3}, M = 58.5

Distance between

A^{+}

and

B^{-}

AB = 269 pm .

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11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 18

Iron has a body centred cubic unit cell with a cell edge of

286 .65 pm

. The density of iron is

7 .87 g {cm}^{- 3}

. Use this information to calculate avogadro's number (At. mass of

Fe = 56 g {mol}^{- 1}

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11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 19

The well-known mineral fluorite is chemically calcium fluoride. It is well known that in one unit of this mineral, there are

4 {Ca}^{2 +}

ions and

8 F^{-}

ions, and that

{Ca}^{2 +}

ions are arranged in a

fcc

lattice. The

F^{-}

ions fill all the tetrahedral holes in the face-centred cubic lattice of

{Ca}^{2 +}

ions. The edge of the unit cell is

5 .46 \times 10^{- 8} cm

in length. The density of the solid is

3 .18 g {cm}^{- 3}

. Use this information to calculate Avogadro's number (Molar mass of

{CaF}_{2}

(Molar mass of

{CaF}_{2} = 78 .08 g {mol}^{- 1}

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11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 20

An element crystallizes in BCC structure. The edge length of its unit cell is

288 pm

. If the density of the crystals is

7 .2 g {cm}^{- 3}

, How many atoms of this element are present in

100 g

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11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 33

A compound

AB

crystallises in bcc lattice with the unit cell edge length of

380 pm

. Calculate the distance between oppositely charged ions in the lattice.

HARD

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 33

A compound

AB

crystallises in bcc lattice with the unit cell edge length of

380 pm

. The distance between oppositely charged ions in the lattice is

329 pm

. Calculate the radius of

B^{-}

if the radius of

A^{+}

190 pm

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11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 36

Aluminium metal forms a cubic close-packed crystal structure. Its atomic radius is

125 \times 10^{- 12} m

. Calculate the length of the side of the unit cell.

HARD

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 6 - States of Matter: Solid State>PROBLEMS FOR PRACTICE>Q 36

Aluminium metal forms a cubic close-packed crystal structure. Its atomic radius is

125 \times 10^{- 12} m

. How many such unit cells are there in

1 .00 m^{3}

of aluminium?

KBr has fcc structure. The density of KBr is 2.75 g cm-3. Find the distance between K+ and Br-. (At mass of Br=80.0).

Important Questions on States of Matter: Solid State

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$KBr$ has $fcc$ structure. The density of $KBr$ is $2 .75 g {cm}^{- 3}$ . Find the distance between $K^{+}$ and ${Br}^{-}$ . (At mass of $Br = 80 .0$ ).