1
MCQ (Single Correct Answer)

NEET 2016 Phase 1

Which one of the following characteristics is associated with adsorption?
A
$$\Delta $$G and $$\Delta $$H are negative but $$\Delta $$S is positive.
B
$$\Delta $$G and $$\Delta $$S are negative but $$\Delta $$H is positive.
C
$$\Delta $$G is negative but $$\Delta $$H and $$\Delta $$S are positive.
D
$$\Delta $$G, $$\Delta $$H and $$\Delta $$S all are negative.

Explanation

Adsorption is spontaneous process, therefore change in the free energy ( $$\Delta $$G) for the process is negative.

As we know that

$$\Delta $$G = $$\Delta $$H – T$$\Delta $$S

S is negative because adhering of gas molecules to the surface lowers the randomness.

$$ \therefore $$ $$\Delta $$G can be –ve only when $$\Delta $$H is –ve.
2
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

Which property of colloidal solution is independent of charge on the colloidal particles?
A
Electro-osmosis
B
Tyndall effect
C
Coagulation
D
Electrophoresis

Explanation

Tyndall effect is the scattering of light by sol particles which cannot be affected by charge on them.
3
MCQ (Single Correct Answer)

AIPMT 2014

Which property of colloids is not dependent on the charge on colloidal particles?
A
Coagulation
B
Electrophoresis
C
Electro-osmosis
D
Tyndall effect

Explanation

Tyndall effect is due to the scattering of light by colloidal particles and not due to the charge.
4
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

The protecting power of lyophilic colloidal sol is expressed in terms of
A
coagulation value
B
gold number
C
critical micelle concentration
D
oxidation number

Explanation

The lyophobic sols are less stable than lyophilic sols. The lyophilic sols are thus used to protect the lyophobic sols. This property of lyophilic sols is known as protective action of lyophilic sols.

Which can be represented by gold number. Lesser the gold number, higher is the protecting power.

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