Question

Calculate the theoretical density for Mgo. Show all your steps and draw the unit cell....

Answer 1

Unit cell of MgO is shown below

Mg + 0000 02-

Theoreticaldensity ion weight in unitcell volume of unit cell

Pth NaMa + NcMc avogadro number * V

Where

Na= number of anion per unit cell(O2-)

Ma= mass if anion = 16 g/mol

Nc = number of cation per unit cell(Mg2+)

Mc = mass 0f cation = 24.305 g/mol

Let us find Na and Nb

Each anion occupy every corner of unit cell (8 corner) and every face center (6 faces)

So

Na = 8*=+6* =1+3=4 2

Each cation occupy edge center (12 edges) and centre of unit cell.

1 Nc= 12 * =+1=3+1=4 4

Now we need to find edge length (a)

By analysing unit cell we get to know

So

a = det da

Where are diameter of cation and anion

de, da

a=det da dea 172 pm da 2.52pm detda 2 252+172 2 424 pm Volume of unut cell raas (424X106033 7.6225x10 - 23 Theoretical Density eth 4 (16+ 24.305) 6.023x10 23x7.6225x10 23 2x80.61 3.512 g/cm3 45.91

Mg + 0000 02-

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