Question

The particles in various forms are visible only under an ultramicroscope. A solution containing such particles is called:
A.True solution
B.Colloidal solution
C.Saturated solution
D.Heterogeneous solution

Answer 1

1.The size of the particles of a colloidal solution is such that they can pass through ordinary filter paper but cannot pass through animal membrane.
2.Ultramicroscope is a microscope which is arranged to study the particles that are too small to be visible under an ordinary microscope.

Complete step by step answer:
1.The size of the colloidal particles is intermediate between that of the particles of a true solution and those of a suspension.
2.A true solution is homogeneous in nature and the size of the particles is less than 1 nanometer. The particles of a true solution can pass through both filter paper and animal membrane. They do not settle and appear as clear and transparent. Hence, they are invisible to both the naked eye and microscope. So, option A is not correct.
3.A colloidal solution is heterogeneous in nature and the size of the particles is between 1 nanometer to 1000 nanometer. They do not settle and appear as translucent. Thus, they are not visible by the naked eye or an ordinary microscope. But the scattering of light by the particles is visible under an ultramicroscope. So, option B is correct.
4.A saturated solution is a solution in which no more solute can be dissolved at the same given temperature. Addition of more solute after the saturation point will result in the formation of a solid precipitate or release of gas. So, option C is not correct.
5.A heterogeneous solution consists of visibly different phases. For example, suspension is a heterogeneous mixture of large particles which can settle on standing and hence are visible both by the naked eye and under a microscope. So, option D is wrong.

Hence, option B is correct.

Note:
1.When viewed through a microscope, colloidal particles are seen moving continuously in a zig-zag way. This is called the Brownian movement.
2.Brownian movement does not depend upon the nature of the colloids but depends upon the size of the colloidal particles and viscosity of the sol.
3.Smaller the size and lesser the viscosity, faster is the movement of the colloidal particles.