Question

A metal has FCC lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g cm-³. The molar mass of metal is (1) 30g mol-¹ (2) 27g mol-¹ (3) 20g mol-¹ (4) 40g mol-¹

Answer 1

Answer:

Given,

edge length (a)=404pm=404×10^-12m

=404×10^-10cm

density (d)=2.72gcm-³

it is also given that the metal has FCC lattice so the numbers of atom(z)=4

We know that,d=zm/Na³; here N=Avogadro's no.

m=molar mass

So,m=dNa³/z

2.72gcm-³×6.022×10²³mol⁻¹×(404×10^-10c. m)³

=>m=----------------------------------------------------

4.

1,080,074,594.04×10^-7gmol⁻¹

=>m=-----------------------------------

4 =>m=270,018,648.509×10^-7gmol⁻¹

=>m=27gmol⁻¹

Hence the required ans is (2)27gmol⁻¹