Question

Q4. The density of gold is 19 g/cc. If
1.9X10-4 g of gold is dispersed in one litre
of water to give a sol having spherical gold
particles of radius 10 nm, then the number
of gold particles per mmº of the sol will be:
a. 1.9 X 1012
b. 6.3 X 1014
c. 6.3 X 1010
d. 2.4 X 106​

Answer 1

Answer:

Answer

Volume of gold present in solution,

=DensityofgoldMassofgold=19g/cm31.9×10−4g=0.1×10−4cm3

For spherical particles of gold with a radius equal to 10nm

The volume of each particle:

34πr3=34×722×(10×10−7cm)3

=2188×10−18cm3

Number of gold particles present:

=VolumeofeachparticleVolumeofgoldinsolution

=2188×10−18cm30.1×10−4cm3

=8821×