Mechanism of Adsorption

Q.

What is delta S and delta H?

Q. Which of the following is not applicable to chemisorption?

1. Its heat of adsorption is high
2. It takes place at hight temperature
3. It is reversible
4. Only the monolayer adsorption occurs

Q.

Why adsorption is always exothermic?

Q.

The correct statement(s) about surface properties is (are)

1. The critical temperatures of ethane and nitrogen are 563 K and 126 K, respectively. The adsorption of ethane will be more than that of nitrogen of same amount of activated charcoal at a given temperature.

2. Cloud is an emulsion type of colloid in which liquid is dispersed phase and gas is dispersion medium.

3. Adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system.

4. Brownian motion of colloidal particles does not depend on the size of the particles but depends on viscosity of the solution.

Q.

What do you understand by activation of adsorbent? How is it achieved?

Q. Differences between physisorption and chemisorption with detail.

Q. It is found that the equilibrium constant increases by a factor of four when the temperature is increased from ${25}^{\circ }Cto{40}^{\circ }C$. The value of $\Delta H$ is

1. 89.43 kJ
2. 71.67 kJ
3. 25.46 kJ
4. 171.67 kJ

Q. is physical adsorption endothermic or exothermic

Q.

During the adsorption of Krypton on activated charcoal at low temperature, which of the following is true?

1. $\Delta H>0and\Delta S<0$
2. $\Delta H<0and\Delta S<0$
3. $\Delta H>0and\Delta S>0$
4. $\Delta H<0and\Delta S>0$

Q. Which of the following is correct adsorption isobar for physisorption ?
Here,
$\left(\frac{x}{m}\right)$ is extent of adsorption per unit mass of adsorbent

Q. Assertion :For adsorption $\Delta G,\Delta S$ and $\Delta H$ all have negative values. Reason: Adsorption is a spontaneous process accompanied by decrease in randomness.

1. If both (A) and (R) are true and (R) is the correct explanation of (A).
2. If both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. If (A) is correct, but (R) is incorrect.
4. If (A) and (R) are both incorrect.

Q. A freshely prepared $Fe(OH{)}_3$ precipitate is peptized by adding a solution of $FeC{l}_3$. The charge on colloidal particle is due to the preferential adsorption of:

1. $F{e}^{3+}$ ion
2. $C{l}^{-}$ ion
3. $O{H}^{-}$ ion
4. $B{a}^{2+}$ ion

Q. Why is adsorption always exothermic?

Q. The Vander Waal's constant 'a' for the gases $O_2,N_2,N{H}_3$ and C$H_4$ are 1.3, 1.390, 4.170 and 2.253 $L^2$ atm $mo{l}^{-2}$respectively. The gas which can be most easily liquefied is

1. O₂
2. N₂
3. NH₃
4. CH₄

Q. Adsorption of a gas on the surface of solid is generally accompained by a decrease in entropy. Still a spontaneous process. Explain.

Q. Adsorption is accompanied with :

1. decrease in entropy of system
2. the value of $T\Delta$S is negative
3. all of the above
4. decrease in enthalpy

Q. Adsorption is accompanied by:

1. decrease in entropy of the system
2. decrease in enthalpy of the system
3. $T\Delta S$ for the process is negative
4. all of the above

Q. The hydrated salt, $N{a}_{2}S{O}_4.n{H}_{2}O$ undergoes 56% loss in weight on heating and becomes anhydrous. The value of n (approx.) will be :

1. 3
2. 7
3. 10
4. 5

Q. Which of the following is true in respect of adsorption?

1. $△G<0,△S>0,△H<0$
2. $△G<0,△S<0,△H<0$
3. $△G>0,△S>0,△H<0$
4. $△G<0,△S<0,△H>0$

Q. The molecular mass of Mohr's salt, $FeS{O}_4(N{H}_4{)}_{3}S{O}_4\cdot 6H_{2}O$, is $392$. Its equivalent mass is

1. $392$
2. $39.2$
3. $196$
4. $98.0$

Q. Choose the incorrect statement regarding metal sulphide ions?

1. The solution particles are positively charged due to preferential adsorption of metal ions
2. The solution particles are negatively charged due to preferential adsorption of sulphide ions
3. $M{g}^{2+}$ will coagulate the sol more efficiently compared to $N{a}^{+}$
4. The solution need stabilising agents for their preservation

Q. Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.

Q. Which one of the following characteristics is not correct for physical adsorption?

1. Adsorption is spontaneous
2. Adsorption increases with increase in temperature
3. Adsorption on solids is reversible
4. Both enthalpy and entropy of adsorption are negative

Q. Determine whether the reactions with the following $\Delta$H and $\Delta$S values are spontaneous or non-spontaneous. State whether the reactions are exothermic or endothermic.
(a) $\Delta$H$=-110$kJ, $\Delta$S$=+40J{K}^{-1}$ at $400$K
(b) $\Delta$H$=+40$kJ, $\Delta$S$=-120J{K}^{-1}$ at $250$K.

Q.

What are the molecules which concentrate and accumulate on the surface called:

1. adsorbent

2. absoption

3. adsorbtion

4. adsorbate

Q. Statement 1: An endothermic reaction can be spontaneous
Statement 2: Both the enthalpy and the entropy changes affect the Gibbs free-energy change of the reaction.

1. Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

   
   

2. Statement 1 is correct but Statement 2 is not correct.

3. Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

   
   

4. Both the Statement 1 and Statement 2 are not correct.

5. Statement 1 is not correct but Statement 2 is correct.

Q. Statement: Physical adsorption is weaker than chemical adsorption.
Explanation: Activated complex formed during adsorption possess lower energy level in chemisorption as it is more exothermic.

1. Statement is correct but explanation is wrong
2. Statement is wrong but explanation is correct
3. Both statement and explanation are correct and explanation is correct explanation of statement
4. Both statement and explanation are correct but explanation is not correct explanation of statement

Q. The reaction
$SO{Cl}_2+H_{2}O⟶{SO}_2+2HCl$
is endothermic by $49.4kJ$ and exoergonic by $50.8kJ$. What is the factor that makes the reaction to be spontaneous? Calculate the entropy change at $298K$.

Q. What is the difference when a concentrated solution of KCl is shaken with charcoal and when a dilute
solution of KCl is shaken with charcoal?

Q. $5$ g of crystalline salt, when rendered anhydrous, lost $1.89$ g of water. The formula weight of anhydrous salts is $160$. The number of molecules of water of crystallisation in the salt is:

1. $1$
2. $2$
3. $3$
4. $5$