Surface Chemistry
The adsorbent used in adsorption chromatography is/are -
A. silica gel
B. alumina
C. quick lime
D. magnesia
Choose the most appropriate answer from the options given below :
'Adsorption' principle is used for which of the following purification method?
Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : The diameter of colloidal particles in solution should not be much smaller than wavelength of light to show Tyndall effect.
Reason R : The light scatters in all directions when the size of particles is large enough.
In the light of the above statements, choose the correct answer from the options given below:
What happens when a lyophilic sol is added to a lyophobic sol?
Four gases A, B, C and D have critical temperatures $5.3,33.2,126.0$ and $154.3 \mathrm{~K}$ respectively. For their adsorption on a fixed amount of charcoal, the correct order is:
Ferric chloride is applied to stop bleeding because -
The enthalpy change for the adsorption process and micelle formation respectively are
Which of the following represent the Freundlich adsorption isotherms?
Choose the correct answer from the options given below:
In figure, a straight line is given for Freundrich Adsorption ($y=3x+2.505$). The value of $\frac{1}{n}$ and $\log \mathrm{K}$ are respectively.
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Amongst $\mathrm{He}, \mathrm{Ne}, \mathrm{Ar}$ and $\mathrm{Kr}$; 1$\mathrm{g}$ of activated charcoal adsorbs more of $\mathrm{Kr}$.
Reason R: The critical volume $\mathrm{V}_{\mathrm{c}}\left(\mathrm{cm}^{3} \mathrm{~mol}^{-1}\right)$ and critical pressure $\mathrm{P}_{\mathrm{c}}$ (atm) is highest for Krypton but the compressibility factor at critical point $\mathrm{Z}_{\mathrm{c}}$ is lowest for Krypton.
In the light of the above statements, choose the correct answer from the options given below
Match List I with List II
| LIST I | LIST II | ||
|---|---|---|---|
| A. | Physisorption | I. | Single Layer Adsorption |
| B. | Chemisorption | II. | $20-40 \mathrm{~kJ} \mathrm{~mol}^{-1}$ |
| C. | $\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \stackrel{\mathrm{Fe}(\mathrm{s})}{\longrightarrow} 2 \mathrm{NH}_{3}(\mathrm{~g})$ | III. | Chromatography |
| D. | Analytical Application or Adsorption | IV. | Heterogeneous catalysis |
Choose the correct answer from the options given below:
Adding surfactants in non polar solvent, the micelles structure will look like
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : In expensive scientific instruments, silica gel is kept in watch-glasses or in semipermeable membrane bags.
Reason (R) : Silica gel adsorbs moisture from air via adsorption, thus protects the instrument from water corrosion (rusting) and / or prevents malfunctioning.
In the light of the above statements, choose the correct answer from the options given below :
Match List I and List II
| List I | List II | ||
|---|---|---|---|
| A. | Osmosis | I. | Solvent molecules pass through semi permeable membrane towards solvent side. |
| B. | Reverse osmosis | II. | Movement of charged colloidal particles under the influence of applied electric potential towards oppositely charged electrodes. |
| C. | Electro osmosis | III. | Solvent molecules pass through semi permeable membrane towards solution side. |
| D. | Electrophoresis | IV. | Dispersion medium moves in an electric field. |
Choose the correct answer from the options given below :
Which of the following salt solutions would coagulate the colloid solution formed when $\mathrm{FeCl_3}$ is added to $\mathrm{NaOH}$ solution, at the fastest rate?
The variation of the rate of an enzyme catalyzed reaction with substrate concentration is correctly represented by graph :
Statement I : For colloidal particles, the values of colligative properties are of small order as compared to values shown by true solutions at same concentration.
Statement II : For colloidal particles, the potential difference between the fixed layer and the diffused layer of same charges is called the electrokinetic potential or zeta potential.
In the light of the above statements, choose the correct answer from the options given below
Explanation:
To find the coagulating value of $\mathrm{NaCl}$, we need to determine the amount of $\mathrm{NaCl}$ required to coagulate 1 liter (1000 mL) of the $\mathrm{As}_2\mathrm{S}_3$ solution in 2 hours. This can be calculated using the following formula:
$\text{Coagulating value} = \frac{\text{amount of electrolyte required to coagulate 1 L of sol in 2 hours}}{1\ \mathrm{L}}$
To find the amount of $\mathrm{NaCl}$ required to coagulate 200 mL of the $\mathrm{As}_2\mathrm{S}_3$ solution in 2 hours, we can use the formula for the number of moles of $\mathrm{NaCl}$ used:
$n_{\mathrm{NaCl}} = C_{\mathrm{NaCl}} \times V_{\mathrm{NaCl}}$
where $C_{\mathrm{NaCl}}$ is the concentration of $\mathrm{NaCl}$ in moles per liter, and $V_{\mathrm{NaCl}}$ is the volume of $\mathrm{NaCl}$ solution used in liters. Substituting the given values, we get:
$n_{\mathrm{NaCl}} = 0.5\ \mathrm{M} \times 0.02\ \mathrm{L} = 0.01\ \mathrm{mol}$
To find the amount of $\mathrm{NaCl}$ required to coagulate 1 L of the $\mathrm{As}_2\mathrm{S}_3$ solution, we need to scale up the amount of $\mathrm{NaCl}$ used by a factor of 5 (since 5 times the given volume of $\mathrm{NaCl}$ solution is required to make 1 L of the $\mathrm{As}_2\mathrm{S}_3$ solution). This gives:
$n_{\mathrm{NaCl}} = 0.01\ \mathrm{mol} \times 5 = 0.05\ \mathrm{mol}$
The coagulating value of $\mathrm{NaCl}$ can now be calculated as:
$\text{Coagulating value} = \frac{0.05\ \mathrm{mol}}{1\ \mathrm{L}} \times 1000 = 50\ \mathrm{mM}$
Therefore, the coagulating value of $\mathrm{NaCl}$ is $\boxed{50}$ (in millimoles per liter).
The number of correct statements about modern adsorption theory of heterogeneous catalysis from the following is __________
A. The catalyst is diffused over the surface of reactants.
B. Reactants are adsorbed on the surface of the catalyst.
C. Occurrence of chemical reaction on the catalyst's surface through formation of an intermediate.
D. It is a combination of intermediate compound formation theory and the old adsorption theory.
E. It explains the action of the catalyst as well as those of catalytic promoters and poisons.
Explanation:
A. The catalyst is diffused over the surface of reactants.
This statement is incorrect. In heterogeneous catalysis, the catalyst is usually a solid, and the reactants are in a different phase (gas or liquid). The reactants are adsorbed on the catalyst's surface, not the other way around.
B. Reactants are adsorbed on the surface of the catalyst.
This statement is correct. In the adsorption theory of heterogeneous catalysis, reactants are adsorbed onto the surface of the catalyst, where they undergo a chemical reaction.
C. Occurrence of chemical reaction on the catalyst's surface through formation of an intermediate.
This statement is correct. In the adsorption theory, the reaction takes place on the catalyst's surface through the formation of an intermediate species.
D. It is a combination of intermediate compound formation theory and the old adsorption theory.
This statement is correct. The modern adsorption theory of heterogeneous catalysis combines the concepts of intermediate compound formation and the old adsorption theory.
E. It explains the action of the catalyst as well as those of catalytic promoters and poisons.
The modern adsorption theory of heterogeneous catalysis does explain the action of the catalyst. However, the roles of catalytic promoters and poisons are not entirely explained by this theory. The NCERT textbook states that the modern adsorption theory explains the action of the catalyst but does not elaborate on the roles of promoters and poisons.
Therefore, considering the information provided by the NCERT textbook, point E is not entirely correct. There are three correct statements (B, C, and D) about the modern adsorption theory of heterogeneous catalysis.
Coagulating value of the electrolytes $\mathrm{AlCl}_{3}$ and $\mathrm{NaCl}$ for $\mathrm{As}_{2} \mathrm{S}_{3}$ are 0.09 and 50.04 respectively. The coagulating power of $\mathrm{AlCl}_{3}$ is $x$ times the coagulating power of $\mathrm{NaCl}$. The value of $\underline{x}$ is ___________.
Explanation:
The coagulating power of an electrolyte is inversely proportional to its coagulating value. That is,
$ \text{Coagulating power} = \frac{1}{\text{Coagulating value}} $
Therefore, the coagulating power of AlCl₃ is $ \frac{1}{0.09} $
and the coagulating power of NaCl is $ \frac{1}{50.04} $
We are asked to find the factor by which the coagulating power of AlCl₃ is greater than the coagulating power of NaCl. This factor is given by the ratio
$ x = \frac{\text{Coagulating power of AlCl₃}}{\text{Coagulating power of NaCl}} = \frac{\frac{1}{0.09}}{\frac{1}{50.04}} = \frac{50.04}{0.09} $
$ x = \frac{50.04}{0.09} \approx 556.22 $So, the coagulating power of AlCl₃ is approximately 556 times the coagulating power of NaCl.
However, since the problem asks for the nearest integer, the answer would be 556.
The number of colloidal systems from the following, which will have 'liquid' as the dispersion medium, is ___________.
Gem stones, paints, smoke, cheese, milk, hair cream, insecticide sprays, froth, soap lather
Explanation:
For the adsorption of hydrogen on platinum, the activation energy is $30 ~\mathrm{k} ~\mathrm{J} \mathrm{mol}^{-1}$ and for the adsorption of hydrogen on nickel, the activation energy is $41.4 ~\mathrm{k} ~\mathrm{J} \mathrm{mol}^{-1}$. The logarithm of the ratio of the rates of chemisorption on equal areas of the metals at $300 \mathrm{~K}$ is __________ (Nearest integer)
Given: $\ln 10=2.3$
$\mathrm{R}=8.3 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$
Explanation:
Step 1: Identify Activation Energies
- Activation energy for platinum: $E_{a1} = 30 \, \mathrm{kJ/mol} = 30 \times 10^3 \, \mathrm{J/mol}$
- Activation energy for nickel: $E_{a2} = 41.4 \, \mathrm{kJ/mol} = 41.4 \times 10^3 \, \mathrm{J/mol}$
Step 2: Given Constants
- Gas constant: $R = 8.3 \, \mathrm{J} \, \mathrm{K}^{-1} \mathrm{mol}^{-1}$
- Temperature: $T = 300 \, \mathrm{K}$
- $\ln 10 = 2.3$
Step 3: Calculate Ratio of Rate Constants
Using the Arrhenius equation, the ratio of the rate constants can be calculated as:
$ \frac{K_2}{K_1} = \exp\left(\frac{E_{a1} - E_{a2}}{RT}\right) $
Step 4: Find Logarithm of the Ratio
Taking the natural logarithm and using $\ln 10 = 2.3$ to convert to base-10 logarithm:
$ \log \frac{K_2}{K_1} = \frac{\ln\left(\frac{K_2}{K_1}\right)}{\ln 10} = \frac{E_{a1} - E_{a2}}{2.3 \cdot RT} $
Step 5: Substitute Values
$ \log \frac{K_2}{K_1} = \frac{(30 \times 10^3 - 41.4 \times 10^3) \, \mathrm{J/mol}}{2.3 \times 8.3 \, \mathrm{J} \, \mathrm{K}^{-1} \mathrm{mol}^{-1} \times 300 \, \mathrm{K}} \approx 1.99 $
Step 6: Final Answer
The nearest integer to the calculated value is 2.
So, the logarithm of the ratio of the rates of chemisorption on equal areas of platinum and nickel at 300 K is 2.
Given: $\log 2=0.3010$
Explanation:
$\mathrm{{1 \over n} = \tan (45^\circ )}$
$\therefore$ $\mathrm{n = 1}$
$\mathrm{\log k = 0.602}$
$\therefore$ $\mathrm{k = 4}$
$\mathrm{{x \over m} = k.{p^{1/n}}}$
$ = 4 \times 0.4 = 1.6$ g
Based on the given figure, the number of correct statement/s is/are __________.
A. Surface tension is the outcome of equal attractive and repulsive forces acting on the liquid molecule in bulk.
B. Surface tension is due to uneven forces acting on the molecules present on the surface.
C. The molecule in the bulk can never come to the liquid surface.
D. The molecules on the surface are responsible for vapour pressure if the system is a closed system.
Explanation:
(B) Surface tension is due to uneven forces acting on the molecules present on the surface
(D) The molecules on the surface are responsible for vapor pressure if the system is a closed system
The number of incorrect statement/s from the following is/are ___________
A. Water vapours are adsorbed by anhydrous calcium chloride.
B. There is a decrease in surface energy during adsorption.
C. As the adsorption proceeds, $\Delta$H becomes more and more negative.
D. Adsorption is accompanied by decrease in entropy of the system.
Explanation:
$\to$ When moisture is added in anhydrus CaCl2 then absorption occurs.
$\to$ When silica gel is kept in presence of moisture then it get's wet from outside only so it is a example of adsorption.
Option C :
$\Delta $H is always negative for adsorption. As the adsorption proceeds $\Delta $H becomes less and less negative, ultimately becomes equal to T$\Delta $S and $\Delta $G becomes zero.
So, statements (A) and (C) are incorrect.
The number of statement/s which are the characteristics of physisorption is __________
A. It is highly specific in nature
B. Enthalpy of adsorption is high
C. It decreases with increase in temperature
D. It results into unimolecular layer
E. No activation energy is needed
Explanation:
B. It is low
C. Extent of adsorption decreases with increase of temperature
D. It results in multimolecular layer
E. No activation energy is needed
No. of correct statements $=2$
Given below are the critical temperatures of some of the gases:
| Gas | Critical temperature (K) |
|---|---|
| He | 5.2 |
| CH$_4$ | 190.0 |
| CO$_2$ | 304.2 |
| NH$_3$ | 405.5 |
The gas showing least adsorption on a definite amount of charcoal is
$100 \mathrm{~mL}$ of $5 \%\,(\mathrm{w} / \mathrm{v})$ solution of $\mathrm{NaCl}$ in water was prepared in $250 \mathrm{~mL}$ beaker. Albumin from the egg was poured into $\mathrm{NaCl}$ solution and stirred well. This resulted in a/an :
Match List - I with List - II.
| List - I Reaction |
List - II Catalyst |
||
|---|---|---|---|
| (A) | $4N{H_3}(g) + 5{O_2}(g) \to 4NO(g) + 6{H_2}O(g)$ | (I) | $NO(g)$ |
| (B) | ${N_2}(g) + 3{H_2}(g) \to 2N{H_3}(g)$ | (II) | ${H_2}S{O_4}(l)$ |
| (C) | ${C_{12}}{H_{22}}{O_{11}}(aq) + {H_2}O(l) \to \mathop {{C_6}{H_{12}}{O_6}}\limits_{Glu\cos e} + \mathop {{C_6}{H_{12}}{O_6}}\limits_{Fructose} $ | (III) | $Pt(s)$ |
| (D) | $2S{O_2}(g) + {O_2}(g) \to 2S{O_3}(g)$ | (IV) | $Fe(s)$ |
Choose the correct answer from the options given below :
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 :
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Finest gold is red in colour, as the size of the particles increases, it appears purple then blue and finally gold.
Reason R : The colour of the colloidal solution depends on the wavelength of light scattered by the dispersed particles.
In the light of the above statements, choose the most appropriate answer from the options given below.
For micelle formation, which of the following statements are correct?
A. Micelle formation is an exothermic process.
B. Micelle formation is an endothermic process.
C. The entropy change is positive.
D. The entropy change is negative.
TLC analysis of a mixture having 3 components (A, B, C) using silica gel as the stationary phase gave following Rf values; for A = 0.72, B = 0.48, C = 0.20.
Regarding the above observations, which one of the following statements is not correct for column chromatography of the mixture?
A 42.12% (w/v) solution of NaCl causes precipitation of a certain sol in 10 hours. The coagulating value of NaCl for the sol in 2 hours is :
[Given : Molar mass : Na = 23.0 g mol$-$1 ; Cl = 35.5 g mol$-$1]
Which of the following is a correct statement?
Match List - I with List - II :
| List-I | List-II | ||
|---|---|---|---|
| (A) | negatively charged sol | (I) | $F{e_2}{O_3}\,.\,x{H_2}O$ |
| (B) | macromolecular colloid | (II) | CdS sol |
| (C) | positively charged sol | (III) | Starch |
| (D) | Cheese | (IV) | a gel |
Choose the correct answer from the options given below:
The Zeta potential is related to which property of colloids?
Match List-I with List-II
| List - I | List - II | ||
|---|---|---|---|
| (A) | Lyophilic colloid | (I) | Liquid-liquid colloid |
| (B) | Emulsion | (II) | Protective colloid |
| (C) | Positively charged colloid | (III) | FeCl$_3$ + NaOH |
| (D) | Negatively charged colloid | (IV) | FeCl$_3$ + hot water |
Choose the correct answer from the options given below :
Incorrect statement for Tyndall effect is :
Using very little soap while washing clothes, does not serve the purpose of cleaning of clothes, because :
Given below are two statements :
Statement I : Emulsions of oil in water are unstable and sometimes they separate into two layers on standing.
Statement II : For stabilisation of an emulsion, excess of electrolyte is added.
In the light of the above statements, choose the most appropriate answer from the options given below :
Among the following the number of curves not in accordance with Freundlich adsorption isotherm is ________.
(a) 
(b) 
(c) 
(d) 
Explanation:
100 mL of 0.3 M acetic acid is shaken with 0.8 g of wood charcoal. The final concentration of acetic acid in the solution after adsorption is 0.125 M. The mass of acetic acid adsorbed per gram of carbon is _____________ $\times$ 10$-$4 g.
(Given : Molar mass of acetic acid = 60 g mol$-$1)
Explanation:
$ \begin{aligned} &\text { moles after adsorption }=100 \times 0.125=12.5 \mathrm{~m} \mathrm{~mol} \text {. } \\\\ &\text { moles adsorbed }=30-12.5=17.5 \mathrm{~m} \mathrm{~mol} \end{aligned} $
for acetic acid; weight adsorbed.
$ \begin{aligned} &\text { moles }=\frac{\text { Weight }}{\text { Molar Mass }} \\\\ &\text { weight }=17.5 \times 10^{-3} \times 60=1050 \times 10^{-3} \mathrm{~g} \\\\ &\text { for } 0.8 \mathrm{~g} \text { charcoal mass of acetic acid adsorbed } \\\\ &=1050 \times 10^{-3} \mathrm{~g} \\\\ &1 \mathrm{~g} \text { charcoal }=\frac{1050 \times 10^{-3}}{0.8}=1312.5 \times 10^{-3} \mathrm{~g} \\\\ &=13125 \times 10^{-4} \mathrm{~g} \end{aligned} $
If the initial pressure of a gas is 0.03 atm, the mass of the gas adsorbed per gram of the adsorbent is ___________ $\times$ 10$-$2 g.
Explanation:
$\therefore \mathrm{K}=4$
Slope $=\frac{1}{\mathrm{n}}=1$
and initial pressure $=0.03 \mathrm{~atm}$
$\frac{x}{m}=K(p)^{1 / n}=4 \times 0.03=0.12=12 \times 10^{-2}$
mass of gas absorbed per gm of adsorbent
$ =12 \times 10^{-2} \mathrm{~g} $
When 200 mL of 0.2 M acetic acid is shaken with 0.6 g of wood charcoal, the final concentration of acetic acid after adsorption is 0.1 M. The mass of acetic acid adsorbed per gram of carbon is ____________ g.
Explanation:
Initial moles of acetic acid $=0.2 \times 0.2=0.04$
Final moles of acetic acid $\quad=0.1 \times 0.2=0.02$
Moles of acetic acid adsorbed $=0.04-0.02 = 0.02$
Mass of acetic acid adsorbed per gm of charcoal
$ =\frac{0.02 \times 60}{0.6}=2.0 \mathrm{~g} $
Choose the most appropriate answer from the options given below.
(x - mass of the gas absorbed ; m - mass of adsorbent ; P - pressure)
