Chapter 19

Which of the following is not an example of heterogeneous catalytic reaction?(a) Ostwald's process (b) Combustion of coal (c) Hydrogenatoin of vegetable oils (d) Haber's process

Amongst the following statements regarding adsorption, those that are valid are :(1) \(\Delta \mathrm{H}\) becomes less negative as adsorption proceeds. (2) On a given adsorbent, ammonia is adsorbed more than nitrogen gas. (3) On adsorption, the residual force acting along the surface of the adsorbent increases. (4) With increase in temperature, the equilibrium concentration of adsorbate increases. (a) (4) and (1) (b) (2) and (3) (c) (1) and (2) (d) (3) and (4)

Identify the correct statement regarding enzymes(a) Enzymes are specific biological catalysts that cannot be poisoned (b) Enzymes are normally heterogeneous catalysts that are very specific in their action (c) Enzymes are specific biological catalysts that can normally function at very high temperatures ( \(\mathrm{T} \sim 1000 \mathrm{~K}\) ) (d) Enzymes are specific biological catalysts that possess well-defined active sites

Match the catalysts to the correct processes:Catalyst Process (A) \(\mathrm{TiCl}_{4}\) (i) Wacker process (B) \(\mathrm{PdCl}_{2}\) (ii) Ziegler - Natta polymerization (C) \(\mathrm{CuCl}_{2}\) (iii) Contact process (D) \(\mathrm{V}_{2} \mathrm{O}_{5}\) (iv) Deacon's process (a) (A) - (ii), (B) - (iii), (C) - (iv), (D) - (i) (b) (A) - (iii), (B)-(i), (C) - (ii), (D) - (iv) (c) (A) - (iii), (B)-(ii), (C) - (iv), (D) - (i) (d) (A) - (ii), (B) - (i), (C) - (iv), (D) - (iii)

A sample of red ink (a colloidal suspension) is prepared by mixing eosin dye, egg white, HCHO and water. The component which ensures stabilitiy of the ink sample is :(a) Egg white (b) Water (c) \(\mathrm{HCHO}\) (d) Eosin dye

Adsorption of a gas follows Freundlich adsorption isotherm. \(x\) is the mass of the gas adsorbed on mass \(\mathrm{m}\) of the adsorbent. The plot of \(\frac{x}{m}\) versus \(\log p\) is shown in the given graph. \(\frac{x}{m}\) is proportional to :(a) \(p^{2 / 3}\) (b) \(p^{3 / 2}\) (c) \(p^{3}\) (d) \(p^{2}\)

Tyndall effect is observed when :(a) The diameter of dispersed particles is much larger than the wavelength of light used. (b) The diameter of dispersed particles is much smaller than the wavelength of light used. (c) The refractive index of dispersed phase is greater than that of the dispersion medium. (d) The diameter of dispersed particles is similar to the wavelength of light used.

Given gas critical temperature/ \(\mathrm{K}\) for\(\mathrm{H}_{2} \mathrm{CH}_{4} \mathrm{CO}_{2} \quad \mathrm{SO}_{2}\) is \(\begin{array}{llll}33 & 190 & 304 & 630\end{array}\) On the basis of data given above, predict which of the following gases shows least adsorption on a definite amount of charcoal?(a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{CH}_{4}\) (c) \(\mathrm{CO}_{2}\) (d) \(\mathrm{H}_{2}\)

If \(x\) gram of gas is adsorbed by \(m\) gram of adsorbent at pressure \(P\), the plot of \(\log \frac{x}{m}\) versus \(\log P\) is linear. The slope of the plot is: (n and \(k\) are constants and \(\mathrm{n}>1\) )(a) \(\log \mathrm{k}\) (b) \(\frac{1}{n}\) (c) \(2 \mathrm{k}\) (d) \(\mathrm{n}\)

Which of the following is used for the preparation of colloids?(a) Ostwald Process (b) Van Arkel Method (c) Bredig's Arc Method (d) Mond Process

Adsorption of a gas on a surface follows Freundlich adsorption isotherm. Plot of \(\log \frac{x}{m}\) versus \(\log p\) gives a straight line with slope equal to \(0.5\), then :( \(\frac{x}{m}\) is the mass of the gas adsorbed per gram of adsorbent)(a) Adsorption is independent of pressure. (b) Adsorption is proportional to the pressure. (c) Adsorption is proportional to the square root of pressure. (d) Adsorption is proportional to the square of pressure.

The size of a raw mango shrinks to a much smaller size when kept in a concentrated salt solution. Which one of the following processes can explain this?(a) Osmosis (b) Dialysis (c) Diffusion (d) Reverse osmosis

For a linear plot of \(\log (x / m)\) versus \(\log p\) in a Freundlich adsorption isotherm, which of the following statements is correct? ( \(k\) and \(n\) are constants).(a) Only \(1 / n\) appears as the slope. (b) \(\log (1 / n)\) appears as the intercept. (c) Both \(k\) and \(1 / n\) appear in the slope term. (d) \(1 / n\) appears as the intercept.

As per Hardy-Schulze formulation, the flocculation values of the following for ferric hydroxide sol are in the order:(a) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]<\mathrm{K}_{2} \mathrm{CrO}_{4}<\mathrm{KBr}=\mathrm{KNO}_{3}=\mathrm{AlCl}_{3}\) (b) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]<\mathrm{K}_{2} \mathrm{CrO}_{4}<\mathrm{AlCl}_{3}<\mathrm{KBr}<\mathrm{KNO}_{3}\) (c) \(\mathrm{AlCl}_{3}>\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]>\mathrm{K}_{2} \mathrm{CrO}_{4}>\mathrm{KBr}=\mathrm{KNO}_{3}\) (d) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]>\mathrm{AlCl}_{3}>\mathrm{K}_{2} \mathrm{CrO}_{4}>\mathrm{KBr}>\mathrm{KNO}_{3}\)

A particular adsorption process has the following characteristics : (i) It arises due to van der Waals forces and (ii) it is reversile. Identify the correct statement that describes the above adsorption process:(a) Adsorption is monolayer. (b) Adsorption increases with increase in temperature. (c) Enthalpy of adsorption is greater than \(100 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (d) Energy of activation is low.

Peptization is a :(a) process of bringing colloidal molecule into solution (b) process of converting precipitate into colloidal solution (c) process of converting a colloidal solution into precipitate (d) process of converting soluble particles to form colloidal solution

The following statements relate to the adsorption of gases on a solid surface. Identify the incorrect statement among them :(a) Enthalpy of adsorption is negative (b) Energy appears as heat (c) On adsorption, the residual forces on the surface are increased (d) Entropy of adsorption is negative

The correct option among the following is :(a) Colloidal medicines are more effective because they have small surface area. (b) Addition of alum to water makes it unfit for drinking(c) Colloidal particles in lyophobic sols can be precipitated by electrophoresis. (d) Brownian motion in colloidal solution is faster if the viscosity of the solution is very high.

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

Adsorption of gases on solid surface is generally exothermic because(a) enthalpy is positive (b) entropy decreases (c) entropy increases (d) free energy increases

Among the colloids cheese (C), milk (M) and smoke (S), the correct combination of the dispersed phase and dispersion medium, respectively is:(a) \(\mathrm{C}\) : liquid in solid; \(\mathrm{M}\) : liquid in solid; \(\mathrm{S}\) : solid in gas (b) \(\mathrm{C}\) : liquid in solid; \(\mathrm{M}\) : liquid in liquid; \(\mathrm{S}\) : solid in gas (c) C : solid in liquid; M : liquid in liquid; \(\mathrm{S}\) : gas in solid (d) \(\mathrm{C}\) : solid in liquid; \(\mathrm{M}\) : solid in liquid; \(\mathrm{S}\) : solid in gas

Rate of physisorption increases with(a) decrease in temperature (b) increase in temperature (c) decrease in pressure (d) decrease in surface area

Haemoglobin and gold sol are examples of:(a) positively and negatively charged sols, respectively (b) positively charged sols (c) negatively charged sols (d) negatively and positively charged sols, respectively

The mass of gas adsorbed, \(x\), per unit mass of adsorbate, \(m\), was measured at various pressures, \(p .\) A graph between \(\log \frac{x}{m}\) and \(\log p\) gives a straight line with slope equal to 2 and the intercept equal to \(0.4771 .\) The value of \(\frac{x}{m}\) at a pressure of \(4 \mathrm{~atm}\) is : (Given \(\log 3=\) \(0.4771)\)

For coagulation of arsenious sulphide sol, which one of the following salt solution will be most effective?(a) \(\mathrm{BaCl}_{2}\) (b) \(\mathrm{A} 1 \mathrm{Cl}_{3}\) (c) \(\mathrm{NaCl}\) (d) \(\mathrm{Na}_{3} \mathrm{PO}_{4}\)

\(20 \%\) of surface sites are occupied by \(\mathrm{N}_{2}\) molecules. The density of surface site is \(6.023 \times 10^{14} \mathrm{~cm}^{-2}\) and total surface area is \(1000 \mathrm{~cm}^{2}\). The catalyst is heated to \(300 \mathrm{~K}\) while \(\mathrm{N}_{2}\) is completely desorbed into a pressure of \(0.001\) atm and volume of \(2.46 \mathrm{~cm}^{3}\). Find the number of active sites occupied by each \(\mathrm{N}_{2}\) molecule.

Which of the following statements about colloids is false?(a) When silver nitrate solution is added to potassium iodide solution, a negatively charged colloidal solution is formed (b) Freezing point of colloidal solution is lower than true solution at same concentration of a solute (c) Colloidal particles can pass through ordinary filter paper (d) When excess of electrolyte is added to colloidal solution, colloidal particle will be precipitated

The Tyndall effect is observed only when following conditions are satisfied :(i) The diameter of the dispersed particles is much smaller than the wavelength of the light used. (ii) The diameter of the dispersed particle is not much smaller than the wavelength of the light used. (iii) The refractive indices of the dispersed phase and dispersion medium are almost similar in magnitude. (iv) The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude. (a) (i) and (iv) (b) (ii) and (iv) (c) (i) and (iii) (d) (ii) and (iii)

When \(\mathrm{O}_{2}\) is adsorbed on a metallic surface, electron transfer occurs from the metal to \(\mathrm{O}_{2}\). The true statement(s) regarding this adsorption is(are)(a) \(\mathrm{O}_{2}\) is physisorbed (b) Heat is released (c) Occupancy of \(\pi^{*} 2 \rho\) of \(\mathrm{O}_{2}\) is increased (d) Bond length of \(\mathrm{O}_{2}\) is increased

Among the following, correct statement is :(a) Brownian movement is more pronounced for smaller particles than for bigger-particles. (b) Sols of metal sulphides are lyophilic. (c) Hardy Schulze law states that bigger the size of the ons, the greater is its coagulating power. (d) One would expect charcoal to adsorb chlorine more than hydrogen sulphide.

The correct statement(s) pertaining to the adsorption of a gas on a solid surface is (are)(a) Adsorption is always exothermic (b) Physisorption may transform into chemisorption at high temperature (c) Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature (d) Chemisorption is more exothermic than physiosorption, however it is very slow due to higher energy of activation

Under ambient conditions, which among the following surfactants will form micelles in aqueous solution at lowest molar concentration?(a) \(\mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{8}-\mathrm{COO}^{-} \mathrm{Na}^{+}\) (b) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{11} \oplus{\mathrm{N}}{\oplus}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Br}^{-}\) (c) \(\mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{13}-\mathrm{OSO}_{3} \mathrm{Na}^{+}\) (d) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{15} \oplus{\mathrm{N}}{\oplus}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Br}^{-}\)

\(\begin{array}{ll}1 \mathrm{~g} \text { of charcoal adsorbs } 100 \mathrm{~mL} & 0.5 \mathrm{M} \\ \mathrm{CH}_{3} \mathrm{COOH}\end{array}\) to form a monolayer, and thereby the molarity of \(\mathrm{CH}_{3} \mathrm{COOH}\) reduces to \(0.49\). Calculate the surface area of the charcoal adsorbed by each molecule of acetic acid. Surface area of charcoal \(=3.01 \times 10^{2} \mathrm{~m}^{2} / \mathrm{g}\).

The coagulating power of electrolytes having ions \(\mathrm{Na}^{+}, \mathrm{Al}^{3+}\) and \(\mathrm{Ba}^{2+}\) for arsenic sulphide sol increases in the order(a) \(\mathrm{Al}^{3+}<\mathrm{Ba}^{2+}<\mathrm{Na}^{+}\) (b) \(\mathrm{Na}^{+}<\mathrm{Ba}^{2+}<\mathrm{Al}^{3+}\) (c) \(\mathrm{Ba}^{2+}<\mathrm{Na}^{+}<\mathrm{Al}^{3+}\) (d) \(\mathrm{Al}^{3+}<\mathrm{Na}^{+}<\mathrm{Ba}^{2+}\)

The migration of dispersion medium under the influence of an electric potential is called :(a) Cataphoresis (b) Electroosmosis (c) Electrophoresis (d) Sedimentation

Smoke is an example of :(a) Solid dispersed in solid(b) Gas dispersed in liquid (c) Solid dispersed in gas (d) Gas dispersed in solid

Among the electrolytes \(\mathrm{Na}_{2} \mathrm{SO}_{4}, \mathrm{CaCl}_{2}, \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\) and \(\mathrm{NH}_{4} \mathrm{Cl}\), the most effective coagulating agent for \(\mathrm{Sb}_{2} \mathrm{~S}_{3}\) sol is(a) \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) (b) \(\mathrm{CaCl}_{2}\) (c) \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\) (d) \(\mathrm{NH}_{4} \mathrm{Cl}\)

Among the following, the surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient condition is :(a) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{15} \mathrm{~N}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Br}^{-}\) (b) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{11} \mathrm{OSO}_{3} \mathrm{Na}^{+}\) (c) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{COO}^{-} \mathrm{Na}^{+}\) (d) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{11} \mathrm{~N}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Br}\)

Lyophilic sols are(a) Irreversible sols (b) They are prepared from inorganic compound (c) Coagulated by adding electrolytes (d) Self-stabilizing

The correct statement(s) about surface properties is (are)(a) Adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system (b) The critical temperatures of ethane and nitrogen are \(563 \mathrm{~K}\) and \(126 \mathrm{~K}\), respectively. The adsorption of ethane will be more than that of nitrogen on same amount of activated charcoal at a given temperature (c) Cloud is an emulsion type of colloid in which liquid is dispersed phase and gas is dispersion medium (d) Brownian motion of colloidal particles does not depend on the size of the particles but depends on viscosity of the solution.

Choose the correct reason(s) for the stability of the lyophobic colloidal particles.(a) Preferential adsorption of ions on their surface from the solution. (b) Preferential adsorption of solvent on their surface from the solution. (c) Attraction between different particles having opposite charges on their surface. (d) Potential difference between the fixed layer and the diffused layer of opposite charges around the colloidal particles.

Assertion : Micelles are formed by surfactant molecules above the critical micellar concentration (CMC).