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CBSE Class 12-science Answered

How is the ideal density of a substance calculated from unit cell data?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
answered-by-expert Expert Answer
The density of a substance is    defined as the ratio of its mass to its volume. 
 Density = mass/ volume the density of the metal, we can calculate the mass of the atoms in the unit cell. The determination of the mass of a single atom gives an accurate method of determination of Avogadro constant. Suppose, edge length of a unit cell of a cubic crystal determined by X-ray diffraction is a, d the density of the solid substance and M the molar mass/ aomic mass and z is the number of atoms present in the unit cell. Volume of a unit cell = a3 and Mass of the unit cell now connect the volume and mass of a substance to calculate density.
 d = zM / a3NA.
 
            Therefore, density of the unit cell = mass of unit cell / volume of unit cell.
           

Remember the density of the unit cell is the same as the density of the substance.

Answered by | 04 Jun, 2014, 03:23: PM

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