Acidic ferric chloride solution on treatment with excess of potassium ferrocyanide gives a Prussian blue coloured colloidal species. It is :
A
Fe4[Fe(CN)6]3
B
K5Fe[Fe(CN)6]2
C
HFe[Fe(CN)6]
D
KFe[Fe(CN)6]
Explanation
2
JEE Main 2021 (Online) 26th August Evening Shift
MCQ (Single Correct Answer)
The sol given below with negatively charged colloidal particles is :
A
FeCl3 added to hot water
B
KI added to AgNO3 solution
C
AgNO3 added to KI solution
D
Al2O3.xH2O in water
Explanation
When AgNO3
is added to KI,
Iodide ion gets adsorbed on the surface of AgI. This will result in
formation of negatively charged colloids.
When KI is added to AgNO3
following reaction takes place.
Silver cation gets adsorbed on surface of AgI, resulting in
formation of positively charged colloids.
3
JEE Main 2021 (Online) 25th July Evening Shift
MCQ (Single Correct Answer)
Match List I with List II :
List-I Example of colloids
List - II Classification
(a) Cheese
(i) dispersion of liquid in liquid
(b) Pumice stone
(ii) dispersion of liquid in gas
(c) Hair cream
(iii) dispersion of gas in solid
(d) Cloud
(iv) dispersion of liquid in solid
Choose the most appropriate answer from the options given below
A
(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
B
(a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
C
(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
D
(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
Explanation
Cheese $$\to$$ liquid in solid
Pumice stone $$\to$$ gas in solid
Hair cream $$\to$$ liquid in liquid
Cloud $$\to$$ liquid in gas
4
JEE Main 2021 (Online) 20th July Morning Shift
MCQ (Single Correct Answer)
The conditions given below are in the context of observing Tyndall effect in colloidal solutions :
(A) The diameter of the colloidal particles is comparable to the wavelength of light used.
(B) The diameter of the colloidal particles is much smaller than the wavelength of light used.
(C) The diameter of the colloidal particles is much larger than the wavelength of light used.
(D) The refractive indices of the dispersed phase and the dispersion medium are comparable.
(E) The dispersed phase has a very different refractive index from the dispersion medium.
Choose the most appropriate conditions from the options given below :
A
(A) and (E) only
B
(C) and (D) only
C
(A) and (D) only
D
(B) and (E) only
Explanation
The phenomenon of scattering of light by colloidal particles as a result of which the path of the
beam becomes visible is called a tyndall effect. Smaller the diameter and similar the magnitude
of refractive indices, lesser is the scattering and hence the tyndall effect and viced-versa. The
diameter of the dispersed phase particle should not be smaller than the wavelength of light
used because they won't be able to scatter the light so, therefore, the diameter of the dispersed
particles should be equal or not much smaller than the wavelength of the light used.
2. The refractive indies (i.e. the ratio of the velocity of light in vacuum to the velocity of light in
any medium) of the dispersed phase and the dispersion medium should differ greatly
in magnitude than only the particles will be able to scatter the light and tyndall effect will be
obersved. On the other hand, if the refractive indices of the dispersed phase and dispersion
medium are almost similar in magnitude, then there will be no-scattering of light and hence,
therefore, no Tyndall effect effect is observed.
Hence answer (A) and (E) are correct.
Questions Asked from Colloidal State
On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
