Surface Chemistry

NEET Chemistry · 98 questions · Page 7 of 10 · Click an option or "Show Solution" to reveal answer

Q61

Amongst the following statements regarding adsorption, those that are valid are (a)

\Delta

H becomes less negative as adsorption proceeds (b) On a given adsorbent, ammonia is adsorbed more than nitrogen gas (c) On adsorption, the residual force acting along the surface of the adsorbent increases (d) With increase in temperature, the equilibrium concentration of adsorbate increases

A (c) and (d)

B (a) and (b)

C (d) and (a)

D (b) and (c)

Correct Answer

Option B

Solution

(a) Since adsorption is exothermic process, as adsorption proceeds number of active sites present over adsorbent decreases, so less heat is evolved. (b) Since NH3 has higher force of attraction on adsorbent due to its polar nature. (c) As the adsorption increases, residual forces over surface decreases. (d) Since process is exothermic, on increasing temperature it shift to backward direction, so concentration of adsorbate particle decreases.

Q62

Which of the following is used for the preparation of colloids?

A Van Arkel Method

B Bredig’s Arc Method

C Mond Process

D Ostwald Process

Correct Answer

Option B

Solution

Bredig's arc method is used for the preparation of colloids.

Q63

The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged, respectively, which of the following statements is NOT correct?

A magnesium chloride solution coagulates, the gold sol more readily than the iron (III) hydroxide sol.

B sodium sulphate solution causes coagulation in both sols

C mixing the sols has no effect

D coagulation in both sols can be brought about by electrophoresis

Correct Answer

Option C

Solution

When oppositely charged sols are mixed their charges are neutralised.

Both sols may be partially or completely precipitated.

Q64

The aerosol is a kind of colloid in which :

A solid is dispersed in gas

B gas is dispersed in solid

C gas is dispersed in liquid

D liquid is dispersed in water

Correct Answer

Option A

Solution

In aerosol, the dispersion medium is gas while the dispersed phase can be both solid or liquid.

Q65

Kraft temperature is the temperature :

A below which the aqueous solution of detergents starts freezing.

B above which the formation of micelles takes place.

C below which the formation of micelles takes place.

D above which the aqueous solution of detergents starts boiling.

Correct Answer

Option B

Solution

Above Kraft temperature(Tk) the formation of micelles takes place.

Q66

According to Freundlich adsorption isotherm, which of the following is correct ?

{x \over m} \propto {p^0}

{x \over m} \propto {p^1}

{x \over m} \propto {p^{1/n}}

D All the above are correct for different ranges of pressure

Correct Answer

Option D

Solution

The Freundlich adsorption isotherm is mathematically represented as

{x \over m} = k{P^{1/n}}

at high pressure

{1 \over n}

= 0 Hence,

x\,/\,m \propto {p^ \circ }

at low pressure

{1 \over n}

= 1 Hence,

x/m\,\, \propto \,\,p'

Q67

The most appropriate method of making egg-albumin sol is :

A Break an egg carefully and transfer the transparent part of the content to 100 mL of 5% w/V saline solution and stir well

B Break an egg carefully and transfer only the yellow part of the content to 100 mL of 5% w/V saline solution and stir well.

C Keep the egg in boiling water for 10 minutes. After removing the shell, transfer the white part of the content to 100 mL of 5% w/V saline solution and homogenize with a mechanical shaker.

D Keep the egg in boiling water for 10 minutes. After removing the shell, transfer the yellow part of the content to 100 mL of 5% w/V saline solutionand homogenize with a mechanical shaker.

Correct Answer

Option A

Solution

Only the transparent part of an egg has albumin.

Q68

As per Hardy-Schulze formulation, the flocculation values of the following for ferric hydroxide sol are in the order :

A AICl3 > K3[Fe(CN)6] > K2CrO4 > KBr = KNO3

B K3[Fe(CN)6] < K2CrO4 < KBr = KNO3 = AlCl3

C K3[Fe(CN)6] < K2CrO4 < AlCl3 < KBr < KNO3

D K3[Fe(CN)6] > AlCl3 > K2CrO4 > KBr > KNO3

Correct Answer

Option B

Solution

Since, Fe(OH)3 is positively charged sol, hence, anionic charge will flocculate.

As per Hardy Schulze rules coagulation power of anion follows the order : Fe(CN)63–

>

CrO42–

>

Cl– = Br– = NO3– Higher the coagulation power lower will be its flocculation value therefore order will be : Fe(CN)63–

<

CrO42–

<

Cl– = Br– = NO3–

Q69

Tyndall effect is observed when:

A The diameter of dispersed particles is similar to the wavelenght of light used.

B The diameter of dispersed particles is much smaller than the wavelength of light used.

C The diameter of dispersed particles is much larger than the wavelength of light used.

D The refractive index of dispersed phase is greater than that of the dispersion medium.

Correct Answer

Option A

Solution

Diameter of dispersed particles should not be much smaller than wavelength of light used.

Q70

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Dissolved substances can be removed from a colloidal solution by diffusion through a parchment paper. Reason (R) : Particles in a true solution cannot pass through parchment paper but the colloidal particles can pass through the parchment paper. In the light of the above statements, choose the correct answer from the options given below :

A Both (A) and (R) are correct and (R) is the correct explanation of (A)

B Both (A) and (R) are correct but (R) is not the correct explanation of (A)

C (A) is correct but (R) is not correct

D (A) is not correct but (R) is correct

Correct Answer

Option C

Solution

Parchment paper is a semi-permeable membrane which allows particles of true solution to pass through as their size are too small.

Assertion is correct but reason is incorrect.

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