Q1Multiple choice
Which of the following process does not occur at the interface of phases?
- (i)crystallisation
- (ii)heterogenous catalysis
- (iii)homogeneous catalysis
- (iv)corrosion
Show answer
(iii) homogeneous catalysis
Chapter 5
Class 12 Chemistry · 81 questions · 81 with answers
Questions
Q2Multiple choice
At the equilibrium position in the process of adsorption ___________.
- (i)∆H > 0
- (ii)∆H = T∆S
- (iii)∆H > T∆S
- (iv)∆H < T∆S
Show answer
(ii) ∆H = T∆S
Q3Multiple choice
Which of the following interface cannot be obtained?
- (i)liquid-liquid
- (ii)solid-liquid
- (iii)liquid-gas
- (iv)gas-gas
Show answer
(iv) gas-gas
Q4Multiple choice
The term ‘sorption’ stands for ____________.
- (i)absorption
- (ii)adsorption
- (iii)both absorption and adsorption
- (iv)desorption
Show answer
(iii) both absorption and adsorption
Q5Multiple choice
Extent of physisorption of a gas increases with ___________.
- (i)increase in temperature.
- (ii)decrease in temperature.
- (iii)decrease in surface area of adsorbent.
- (iv)decrease in strength of van der Waals forces.
Show answer
(ii) decrease in temperature.
Q6Multiple choice
Extent of adsorption of adsorbate from solution phase increases with ________.
- (i)increase in amount of adsorbate in solution.
- (ii)decrease in surface area of adsorbent.
- (iii)increase in temperature of solution.
- (iv)decrease in amount of adsorbate in solution.
Show answer
(i) increase in amount of adsorbate in solution.
Q7Multiple choice
Which one of the following is not applicable to the phenomenon of adsorption?
- (i)∆H > 0
- (ii)∆G < 0
- (iii)∆S < 0
- (iv)∆H < 0
Show answer
(i) ∆H > 0
Q8Multiple choice
Which of the following is not a favourable condition for physical adsorption?
- (i)high pressure
- (ii)negative ∆H
- (iii)higher critical temperature of adsorbate
- (iv)high temperature
Show answer
(iv) high temperature
Q9Multiple choice
Physical adsorption of a gaseous species may change to chemical adsorption with ______________.
- (i)decrease in temperature
- (ii)increase in temperature
- (iii)increase in surface area of adsorbent
- (iv)decrease in surface area of adsorbent
Show answer
(ii) increase in temperature
Q10Multiple choice
In physisorption adsorbent does not show specificity for any particular gas because ______________.
- (i)involved van der Waals forces are universal.
- (ii)gases involved behave like ideal gases.
- (iii)enthalpy of adsorption is low.
- (iv)it is a reversible process.
Show answer
(i) involved van der Waals forces are universal.
Q11Multiple choice
Which of the following is an example of absorption?
- (i)Water on silica gel
- (ii)Water on calcium chloride
- (iii)Hydrogen on finely divided nickel
- (iv)Oxygen on metal surface
Show answer
(ii) Water on calcium chloride
Q12Multiple choice
On the basis of data given below predict which of the following gases shows least adsorption on a definite amount of charcoal? Gas CO2 SO2 CH4 H2 Critical temp./K 304 630 190 33
- (i)CO2
- (ii)SO2
- (iii)CH4
- (iv)H2
Show answer
(iv) H2
Q13Multiple choice
In which of the following reactions heterogenous catalysis is involved? (a) NO(g) 2SO2 (g) + O2 (g) → 2SO3 (g) (b) Pt(s) 2SO2 (g) → 2SO3 (g) (c) Fe(s) N2 (g) + 3H2 (g) → 2NH3 (g) (d) HCl(l) CH3COOCH3 (l) + H2O (l) → CH3COOH (aq) + CH3OH (aq)
- (i)(b), (c)
- (ii)(b), (c), (d)
- (iii)(a), (b), (c)
- (iv)(d)
Show answer
(i) (b), (c)
Q14Multiple choice
At high concentration of soap in water, soap behaves as ____________.
- (i)molecular colloid
- (ii)associated colloid
- (iii)macromolecular colloid
- (iv)lyophilic colloid
Show answer
(ii) associated colloid
Q15Multiple choice
Which of the following will show Tyndall effect?
- (i)Aqueous solution of soap below critical micelle concentration.
- (ii)Aqueous solution of soap above critical micelle concentration.
- (iii)Aqueous solution of sodium chloride.
- (iv)Aqueous solution of sugar.
Show answer
(ii) Aqueous solution of soap above critical micelle concentration.
Q16Multiple choice
Method by which lyophobic sol can be protected.
- (i)By addition of oppositely charged sol.
- (ii)By addition of an electrolyte.
- (iii)By addition of lyophilic sol.
- (iv)By boiling.
Show answer
(iii) By addition of lyophilic sol.
Q17Multiple choice
Freshly prepared precipitate sometimes gets converted to colloidal solution by ___________.
- (i)coagulation
- (ii)electrolysis 65 Surface Chemistry
- (iii)diffusion
- (iv)peptisation
Show answer
(iv) peptisation
Q18Multiple choice
Which of the following electrolytes will have maximum coagulating value for + AgI/Ag sol?
- (i)Na2S
- (ii)Na3PO4
- (iii)Na2SO4
- (iv)NaCl
Show answer
(ii) Na3PO4
Q19Multiple choice
A colloidal system having a solid substance as a dispersed phase and a liquid as a dispersion medium is classified as ____________.
- (i)solid sol
- (ii)gel
- (iii)emulsion
- (iv)sol
Show answer
(iv) sol
Q20Multiple choice
The values of colligative properties of colloidal solution are of small order in comparison to those shown by true solutions of same concentration because of colloidal particles __________________.
- (i)exhibit enormous surface area.
- (ii)remain suspended in the dispersion medium.
- (iii)form lyophilic colloids.
- (iv)are comparatively less in number.
Show answer
(iv) are comparatively less in number.
Q21Multiple choice
Arrange the following diagrams in correct sequence of steps involved in the mechanism of catalysis, in accordance with modern adsorption theory.
- (i)a → b → c → d → e
- (ii)a → c → b → d → e
- (iii)a → c → b → e → d
- (iv)a → b → c → e → d
Show answer
(ii) a → c → b → d → e
Q22Multiple choice
Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?
- (i)Emulsification
- (ii)Colloid formation
- (iii)Coagulation
- (iv)Peptisation
Show answer
(iii) Coagulation
Q23Multiple choice
Which of the following curves is in accordance with Freundlich adsorption isotherm?
- (i)
- (ii)
- (iii)
- (iv)
Show answer
(iii)
Q24Multiple choice
Which of the following process is not responsible for the presence of electric charge on the sol particles?
- (i)Electron capture by sol particles.
- (ii)Adsorption of ionic species from solution.
- (iii)Formation of Helmholtz electrical double layer.
- (iv)Absorption of ionic species from solution.
Show answer
(iv) Absorption of ionic species from solution.
Q25Multiple choice
Which of the following phenomenon is applicable to the process shown in the Fig. 5.1?
This question refers to a figure in the original PDF.
- (i)Absorption
- (ii)Adsorption
- (iii)Coagulation
- (iv)Emulsification Fig. 5.1 67 Surface Chemistry
Show answer
(ii) Adsorption
Q26Multiple correct
Which of the following options are correct?
- (i)Micelle formation by soap in aqueous solution is possible at all temperatures.
- (ii)Micelle formation by soap in aqueous solution occurs above a particular concentration.
- (iii)On dilution of soap solution micelles may revert to individual ions.
- (iv)Soap solution behaves as a normal strong electrolyte at all concentrations.
Show answer
(ii) Micelle formation by soap in aqueous solution occurs above a particular concentration.
(iii) On dilution of soap solution micelles may revert to individual ions.
Q27Multiple correct
Which of the following statements are correct about solid catalyst?
- (i)Same reactants may give different product by using different catalysts.
- (ii)Catalyst does not change ∆H of reaction.
- (iii)Catalyst is required in large quantities to catalyse reactions.
- (iv)Catalytic activity of a solid catalyst does not depend upon the strength of chemisorption.
Show answer
(i) Same reactants may give different product by using different catalysts.
(ii) Catalyst does not change ∆H of reaction.
Q28Multiple correct
Freundlich adsorption isotherm is given by the expression = k p n which of the following conclusions can be drawn from this expression.
- (i)When = 0, the adsorption is independent of pressure.
- (ii)When = 0, the adsorption is directly proportional to pressure.
- (iii)When n = 0, vs p graph is a line parallel to x -axis.
- (iv)When n = 0, plot of vs p is a curve.
Show answer
(i) When = 0, the adsorption is independent of pressure.
(iii) When n = 0, vs p graph is a line parallel to x -axis.
Q29Multiple correct
H2 gas is adsorbed on activated charcoal to a very little extent in comparison to easily liquefiable gases due to ____________.
- (i)very strong van der Waal’s interaction.
- (ii)very weak van der Waals forces.
- (iii)very low critical temperature.
- (iv)very high critical temperature.
Show answer
(ii) very weak van der Waals forces.
(iii) very low critical temperature.
Q30Multiple correct
Which of the following statements are correct?
- (i)Mixing two oppositely charged sols neutralises their charges and stabilises the colloid.
- (ii)Presence of equal and similar charges on colloidal particles provides stability to the colloids.
- (iii)Any amount of dispersed liquid can be added to emulsion without destabilising it.
- (iv)Brownian movement stabilises sols.
Show answer
(ii) Presence of equal and similar charges on colloidal particles provides stability to the colloids.
(iv) Brownian movement stabilises sols.
Q31Multiple correct
An emulsion cannot be broken by __________ and ___________.
- (i)heating
- (ii)adding more amount of dispersion medium
- (iii)freezing
- (iv)adding emulsifying agent
Show answer
(ii) adding more amount of dispersion medium
(iv) adding emulsifying agent
Q32Multiple correct
Which of the following substances will precipitate the negatively charged emulsions?
- (i)KCl
- (ii)glucose
- (iii)urea
- (iv)NaCl
Show answer
(i) KCl
(iv) NaCl
Q33Multiple correct
Which of the following colloids cannot be coagulated easily?
- (i)Lyophobic colloids.
- (ii)Irreversible colloids.
- (iii)Reversible colloids.
- (iv)Lyophilic colloids.
Show answer
(iii) Reversible colloids.
(iv) Lyophilic colloids.
Q34Multiple correct
What happens when a lyophilic sol is added to a lyophobic sol?
- (i)Lyophobic sol is protected.
- (ii)Lyophilic sol is protected.
- (iii)Film of lyophilic sol is formed over lyophobic sol.
- (iv)Film of lyophobic sol is formed over lyophilic sol.
Show answer
(i) Lyophobic sol is protected.
(iii) Film of lyophilic sol is formed over lyophobic sol.
Q35Multiple correct
Which phenomenon occurs when an electric field is applied to a colloidal solution and electrophoresis is prevented?
- (i)Reverse osmosis takes place.
- (ii)Electroosmosis takes place.
- (iii)Dispersion medium begins to move.
- (iv)Dispersion medium becomes stationary.
Show answer
(ii) Electroosmosis takes place.
(iii) Dispersion medium begins to move.
Q36Multiple correct
In a reaction, catalyst changes ____________.
- (i)physically
- (ii)qualitatively
- (iii)chemically
- (iv)quantitatively
Show answer
(i) physically
(ii) qualitatively
Q37Multiple correct
Which of the following phenomenon occurs when a chalk stick is dipped in ink?
- (i)adsorption of coloured substance
- (ii)adsorption of solvent
- (iii)absorption and adsorption both of solvent
- (iv)absoprtion of solvent 69 Surface Chemistry
Show answer
(i) adsorption of coloured substance
(iv) absoprtion of solvent 69 Surface Chemistry
Q38Short answer
Why is it important to have clean surface in surface studies?
Show answer
It is important to have clean surface as it facilitates the adsorption of desired species.
Q39Short answer
Why is chemisorption referred to as activated adsorption?
Show answer
Chemisorption involves formation of bond between gaseous molecules/ atoms and the solid surface for which high activation energy is required. Thus it is referred to as activated adsorption.
Q40Short answer
What type of solutions are formed on dissolving different concentrations of soap in water?
Show answer
At lower concentration soap forms a normal electrolytic solution with water. After a certain concentration called critical micelle concentration, colloidal solution is formed.
Q41Short answer
What happens when gelatin is mixed with gold sol?
Show answer
Gold sol is a lyophobic sol. Addition of gelatin stabilises the sol.
Q42Short answer
How does it become possible to cause artificial rain by spraying silver iodide on the clouds?
Show answer
Clouds are colloidal in nature and carry charge. Spray of silver iodide, an electrolyte, results in coagulation leading to rain.
Q43Short answer
Gelatin which is a peptide is added in icecreams. What can be its role?
Show answer
Icecreams are emulsions which get stabilised by emulsifying agents like gelatin.
Q44Short answer
What is collodion?
Show answer
It is a 4% solution of nitrocellulose in a mixture of alcohol and ether.
Q45Short answer
Why do we add alum to purify water?
Show answer
The colloidal impurities present in water get coagulated by added alum, thus making water potable.
Q46Short answer
What happens when electric field is applied to colloidal solution?
Show answer
The charged colloidal particles start moving towards oppositely charged electrodes.
Q47Short answer
What causes brownian motion in colloidal dispersion?
Show answer
Unbalanced bombardment of the particles of dispersed phase by molecules of dispersion medium causes brownian motion. This stabilises the sol.
Q48Short answer
A colloid is formed by adding FeCl3 in excess of hot water. What will happen if excess sodium chloride is added to this colloid?
Show answer
Positively charged sol of hydrated ferric oxide is formed and on adding excess of NaCl, negatively charged chloride ions coagulate the positively charged sol of hydrated ferric oxide.
Q49Short answer
How do emulsifying agents stabilise the emulsion?
Show answer
The emulsifying agent forms an interfacial layer between suspended particles and the dispersion medium thereby stabilising the emulsion.
Q50Short answer
Why are some medicines more effective in the colloidal form?
Show answer
Medicines are more effective in the colloidal form because of large surface area and are easily assimilated in this form.
Q51Short answer
Why does leather get hardened after tanning?
Show answer
Animal hide is colloidal in nature and has positively charged particles. When it is soaked in tanin which has negatively charged colloidal particles, it results in mutual coagulation taking place.
Q52Short answer
How does the precipitation of colloidal smoke take place in Cottrell precipitator?
Show answer
In Cottrell precipitator, charged smoke particles are passed through a chamber containing plates with charge opposite to the smoke particles. Smoke particles lose their charge on the plates and get precipitated.
Q53Short answer
How will you distinguish between dispersed phase and dispersion medium in an emulsion?
Show answer
On adding dispersion medium, emulsions can be diluted to any extent. The dispersed phase forms a separate layer if added in excess.
Q54Short answer
On the basis of Hardy-Schulze rule explain why the coagulating power of phosphate is higher than chloride.
Show answer
Minimum quantity of an electrolyte required to cause precipitation of a sol is called its coagulating value. Greater the charge on flocculating ion and smaller is the amount of electrolyte required for precipitation, higher is the coagulating power of coagulating ion (Hardy-Schulze rule).
Q55Short answer
Why does bleeding stop by rubbing moist alum?
Show answer
Moist alum coagulates the blood and so formed blood clot stops bleeding.
Q56Short answer
Why is Fe(OH)3 colloid positively charged, when prepared by adding FeCl3 to hot water?
Show answer
The adsorption of positively charged Fe3+ ions by the sol of hydrated ferric oxide results in positively charged colloid.
Q57Short answer
Why do physisorption and chemisorption behave differently with rise in temperature?
Show answer
Physisorption involves weak van der Waals forces which weaken with rise in temperature. The chemisorption involves formation of chemical bond involving activation energy and like any other chemical reaction is favoured by rise in temperature.
Q58Short answer
What happens when dialysis is prolonged?
Show answer
Due to excessive dialysis, traces of electrolyte which stabilises the colloids is removed completely, making the colloid unstable. As a result coagulation takes place.
Q59Short answer
Why does the white precipitate of silver halide become coloured in the presence of dye eosin.
Show answer
Eosin is adsorbed on the surface of silver halide precipitate making it coloured.
Q60Short answer
What is the role of activated charcoal in gas mask used in coal mines?
Show answer
Activated charcoal acts as an adsorbent for various poisonous gases present in the coal mines.
Q61Short answer
How does a delta form at the meeting place of sea and river water?
Show answer
River water is a colloidal solution of clay and sea water contains lot of electrolytes. The point at which river and sea meet is the site for coagulation. Deposition of coagulated clay results in delta formation.
Q62Short answer
Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.
Show answer
The process of physisorption for example that of H2 on finely divided nickel, involves weak van der Waals’ forces. With increase in temperature, hydrogen molecules dissociate into hydrogen atoms which are held on the surface by chemisorption.
Q63Short answer
Why is desorption important for a substance to act as good catalyst?
Show answer
After the reaction is over between adsorbed reactants, the process of desorption is important to remove products and further create space for the other reactant molecules to approach the surface and react.
Q64Short answer
What is the role of diffusion in heterogenous catalysis?
Show answer
The gaseous molecules diffuse on to the surface of the solid catalyst and get adsorbed. After the required chemical changes the products diffuse away from the surface of the catalyst leaving the surface free for more reactant molecules to get adsorbed and undergo reaction. 75 Surface Chemistry
Q65Short answer
How does a solid catalyst enhance the rate of combination of gaseous molecules?
Show answer
When gaseous molecules come in contact with the surface of a solid catalyst, a weak chemical combination takes place between the surface of the catalyst and the gaseous molecules, which increases the concentration of reactants on the surface. Different moelcules adsorbed side by side have better chance to react and form new molecules. This enhances the rate of reaction. Also, adsorption is an exothermic process. The heat released in the process of adsorption is utilised in enhancing the reaction rate.
Q66Short answer
Do the vital functions of the body such as digestion get affected during fever? Explain your answer.
Show answer
Hint : The optimum temperature range for enzymatic activity is 298- 310 K. On either side of this temperature range, enzymatic activity gets affected. Thus, during fever, when temperature rises above 310 K, the activity of enzymes may be affected. IV. Matching Type
Q67Multiple choice
Method of formation of solution is given in Column I. Match it with the type of solution given in Column II. Column I Column II (i) Sulphur vapours passed
- (a)Normal electrolyte solution through cold water (ii) Soap mixed with water above
- (b)Molecular colloids critical micelle concentration (iii) White of egg whipped with water
- (c)Associated colloid (iv) Soap mixed with water below
- (d)Macro molecular colloids critical micelle concentration
Show answer
(a) Normal electrolyte solution through cold water (ii) Soap mixed with water above
(b) Molecular colloids critical micelle concentration (iii) White of egg whipped with water
(c) Associated colloid (iv) Soap mixed with water below
(d) Macro molecular colloids critical micelle concentration
Q68Multiple choice
Match the statement given in Column I with the phenomenon given in Column II. Column I Column II (i) Dispersion medium moves in
- (a)Osmosis an electric field (ii) Solvent molecules pass through semi
- (b)Electrophoresis permeable membrane towards solvent side (iii) Movement of charged colloidal particles
- (c)Electroosmosis under the influence of applied electric potential towards oppositely charged electrodes (iv) Solvent molecules pass through semi
- (d)Reverse osmosis permeable membranes towards solution side 71 Surface Chemistry
Show answer
(a) Osmosis an electric field (ii) Solvent molecules pass through semi
(c) Electroosmosis under the influence of applied electric potential towards oppositely charged electrodes (iv) Solvent molecules pass through semi
(b) Electrophoresis permeable membrane towards solvent side (iii) Movement of charged colloidal particles
(d) Reverse osmosis permeable membranes towards solution side 71 Surface Chemistry
Q69Multiple choice
Match the items given in Column I and Column II. Column I Column II (i) Protective colloid
- (a)FeCl3 + NaOH (ii) Liquid - liquid colloid
- (b)Lyophilic colloids (iii) Positively charged colloid
- (c)Emulsion (iv) Negatively charged colloid
- (d)FeCl3 + hot water
Show answer
(a) FeCl3 + NaOH (ii) Liquid - liquid colloid
(b) Lyophilic colloids (iii) Positively charged colloid
(c) Emulsion (iv) Negatively charged colloid
(d) FeCl3 + hot water
Q70Multiple choice
Match the types of colloidal systems given in Column I with the name given in Column II. Column I Column II (i) Solid in liquid
- (a)Foam (ii) Liquid in solid
- (b)Sol (iii) Liquid in liquid
- (c)Gel (iv) Gas in liquid
- (d)Emulsion
Show answer
(a) Foam (ii) Liquid in solid
(b) Sol (iii) Liquid in liquid
(c) Gel (iv) Gas in liquid
(d) Emulsion
Q71Multiple choice
Match the items of Column I and Column II. Column I Column II (i) Dialysis
- (a)Cleansing action of soap (ii) Peptisation
- (b)Coagulation (iii) Emulsification
- (c)Colloidal sol formation (iv) Electrophoresis
- (d)Purification
Show answer
(a) Cleansing action of soap (ii) Peptisation
(d) Purification
(b) Coagulation (iii) Emulsification
(c) Colloidal sol formation (iv) Electrophoresis
Q72Multiple choice
Match the items of Column I and Column II. Column I Column II (i) Butter
- (a)dispersion of liquid in liquid (ii) Pumice stone
- (b)dispersion of solid in liquid (iii) Milk
- (c)dispersion of gas in solid (iv) Paints
- (d)dispersion of liquid in solid
Show answer
(a) dispersion of liquid in liquid (ii) Pumice stone
(d) dispersion of liquid in solid
(b) dispersion of solid in liquid (iii) Milk
(c) dispersion of gas in solid (iv) Paints
Q73Assertion & reason
Assertion (A): An ordinary filter paper impregnated with collodion solution stops the flow of colloidal particles.
Reason (R): Pore size of the filter paper becomes more than the size of colloidal particle.
Show answer
Q74Assertion & reason
Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
Show answer
Q75Assertion & reason
Assertion (A): Colloidal solutions do not show brownian motion.
Reason (R): Brownian motion is responsible for stability of sols.
Show answer
(v)
Q76Assertion & reason
Assertion (A): Coagulation power of Al3+ is more than Na+.
Reason (R): Greater the valency of the flocculating ion added, greater is its power to cause precipitation (Hardy Schulze rule).
Show answer
Q77Assertion & reason
Assertion (A): Detergents with low CMC are more economical to use.
Reason (R): Cleansing action of detergents involves the formation of micelles. These are formed when the concentration of detergents becomes equal to CMC.
Show answer
Q78Long answer
What is the role of adsorption in heterogenous catalysis?
Show answer
Hint • reactants are adsorbed on the surface of the catalyst • occurrence of chemical reaction on the surface of catalyst • desorption.
Q79Long answer
What are the applications of adsorption in chemical analysis?
Show answer
Hint: • In TLC • Adsorption indicators. • In qualitative analysis.
Q80Long answer
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
Show answer
Hint: • Adsorption of pine oil on sulphide ore particles. • Formation of emulsion. • Hence ore comes out with froth. • Explanation for shape selective catalysis.
Q81Long answer
What do you understand by shape selective catalysis? Why are zeolites good shape selective catalysts? 73 Surface Chemistry
Show answer
Hint: • Honey comb like structure of zeolites. • Pores provide sites for reactants to react.