A metal has a fcc lattice. The edge length of the unit cell is 404 pm....
Given, cell is fcc, So Z =4
Edge length, a = 404 pm = 4.04 x 10-8 cm
Density of metal, d = 2.72 g cm-3
NA = 6.02 x 1023 mol-1
Molar mass ofg the metal, M =?
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A metal has a fcc lattice. The edge length of the unit cell is 404 pm....
Given Information
- A metal has a fcc lattice
- Edge length of the unit cell = 404 pm
- Density of the metal = 2.72 g cm-3
- Avogadro's number (NA) = 6.02 x 1023mol-1
To Find: Molar mass of the metal
Solution
1. Calculation of Volume of Unit Cell
- In an fcc lattice, there are 4 atoms per unit cell
- The distance between the opposite faces in a cube is equal to the edge length of the cube
- Therefore, the diagonal of a face of the cube is √2 times the edge length
- The diagonal of the cube is also the distance between the centers of two opposite corner atoms
- Hence, the length of the body diagonal of the cube is √3 times the edge length
- The volume of the unit cell can be calculated as follows:
Volume of Unit Cell = (Edge Length)^3 / 4
= (404 pm)^3 / 4
= 26.43 x 10^-24 cm^3
2. Calculation of Mass of One Unit Cell
- The density of the metal is given as 2.72 g cm^-3
- Therefore, the mass of the unit cell can be calculated as follows:
Mass of Unit Cell = Density x Volume of Unit Cell
= 2.72 g cm^-3 x 26.43 x 10^-24 cm^3
= 7.20 x 10^-23 g
3. Calculation of Molar Mass of the Metal
- The mass of one unit cell is equal to the mass of the atoms present in it
- The number of atoms present in one unit cell of an fcc lattice is 4
- Therefore, the mass of one atom can be calculated as follows:
Mass of one atom = mass of unit cell / number of atoms
= 7.20 x 10^-23 g / 4
= 1.80 x 10^-23 g
- The molar mass of the metal can be calculated as follows:
Molar Mass = Mass of one atom x Avogadro's number
= 1.80 x 10^-23 g x 6.02 x 1023 mol^-1
= 27.22 g mol^-1
Therefore, the molar mass of the metal is 27 g mol^-1, which is option 'C'.
A metal has a fcc lattice. The edge length of the unit cell is 404 pm....
Answer is c.. care the unit of edge length ,is cm
...d=zm÷a3.Na