CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 7 - MCQExams.com

Which letter corresponds to the total change in energy for the overall reaction?
524578_2343ece3c2404a98bc220725d073b3ff.png
  • A
  • B
  • C
  • D
  • E
Which of the following is not a solid in liquid colloid type?
  • Gelatin
  • Pigmented ink
  • Blood
  • Jelly
The process of enzyme catalysis of biological processes follows a simple pathway and involves three principal species.
The substrate, which we will represent as S, is the molecule that is to undergo reaction. The enzyme, E, acts as the catalyst, and the product, P, is the result of the reaction.
The substrate, S, attaches to a receptor site on the enzyme, E, where it is held in place as the reaction proceeds. Once reaction is completer, the product, P, is released from the receptor site, along with any remaining portion of the substrate molecule.
The process can be represented as shown below, where S-E represents the substrate, bound to the catalyst. As the product forms, the receptor site on the catalyst is again freed to accept another substrate molecule.
$$S + E \rightarrow [S - E]\rightarrow P + E$$
The reaction rate can be investigated either in terms of decreasing concentration of substrate, or increasing appearance of product.
As part of her senior-year STEM project, Athena designs an experiment to study a particular enzyme-catalyzed reaction. Since the product of the reaction is a colored species, she sets up a colorimetric interface to measure the rate of appearance of the colored product, in units of concentration of product over time: $$\dfrac {mol.L^{-1}}{min}$$, or simply, $$\dfrac {M}{min}$$. The plot of product formation vs time appears below.
By design, Athena's experiment began with a large excess of the substrate, S, relative to the enzyme, E.
Which of the following offers the BEST description of the results of her study?
537698_22fa141ce738477bbfaeac0ff3085b3a.png
  • After initially increasing rapidly, the rate of product formation slows as the system approaches and achieves equilibrium, as shown by the leveling of the graph. The steady level of product formation indicates the equilibrium state, and can be expected to remain at that level indefinitely, barring a change in temperature.
  • Product formation rises rapidly up to the point at which not enough substrate molecules are available to bond to the enzyme's receptor sites. The rate of product formation levels as enzyme molecules await collision with substrate molecules. This level will begin to slowly diminish over time.
  • The reaction proceeds relatively rapidly until the point where the concentrations of enzyme and substrate level out. From there on, reaction rate is steady, and will remain so, so long as both substrate and enzyme remain in the system.
  • The reaction starts off slowly, as substrate and enzyme molecules collide and bind together. The rate of product formation increases as more and more of the receptor sites on the enzyme become occupied and reaction rate picks up.

    Once all the enzyme receptor sites have been occupied, the reaction rate stabilizes, since a particular receptor site only becomes available as the previous reaction at that side goes to completion. Over time, as more and more of the substrate is converted to product, the rate of formation can be expected to decrease.
Cod liver is an example of:
  • oil emulsion
  • oil in water emulsion
  • water in oil emulsion
  • water in water emulsion
Which of these can be one of the uses of colloids?
  • Colloids act as transport vector
  • Colloids are used in intravenous therapy
  • Movement of enzyme molecules in water is because of colloid action
  • All of the above
Soft soaps are:
  • sodium salts of fatty acids
  • potassium salts of fatty acids, containing excess of free alkali
  • potassium salts of fatty acids, containing no free alkali
  • calcium salts of fatty acids
The pollutants released by jet aeroplanes in the atmosphere as chlorofluorocarbons are called:
  • photochemical oxidants
  • photochemical reductants
  • aerosols
  • physical pollutants
Argyrol is a:
  • Ferric oxide sol
  • Silver sol
  • Gold sol
  • Arsenic sol
Soap molecules have two parts - a polar and a non-polar. When soap is added to water:
  • both parts dissolve in water
  • non-polar part dissolves in water
  • polar part dissolves in water
  • both parts remain undissolved in water and form hydrocarbon layer
Hard soaps are:
  • calcium salts of higher fatty acids
  • magnesium salts of higher fatty acids
  • potassium salts of higher fatty acids
  • sodium salts of higher fatty acids
Detergents are better than soaps because:
  • they wash clothes better
  • they absorb the hardness of water
  • they are less affected by hard water
  • they are less soapy
Sulphur sol contains :
  • discrete $$S-$$atoms
  • discrete $$S-$$molecules
  • large aggregates of $$S-$$molecules
  • water dispersed in solid sulphur

Which one of the following is correctly matched?
    • Aerosol-smoke
    • Foam-mist
    • Emulsion-curd
    • All of these
    Soap action is due to:
    • micelle formation
    • colloidal dispersion of micelles in water
    • oil drop dispersal
    • All of these
    Which one of the following is an emulsion?
    • Milk
    • Soap lather
    • Butter
    • Vanishing Cream
    Colloidal sols are more effective for medical purposes because:
    • they have smaller surface area
    • they have larger surface area
    • their assimilation is difficult
    • they can be easily prepared
    Which sol can be prepared directly by mixing the dispersed phase with dispersion medium?
    • Lyophobic sol
    • Lyophilic sol
    • Both
    • None
    Which of the following is an example for heterogeneous catalysis reaction?
    • $$2S{ O }_{ 2 }\left( g \right) +{ O }_{ 2 }\left( g \right) \underrightarrow { \quad \quad NO\left( g \right) \quad \quad } 2S{ O }_{ 3 }\left( g \right) $$
    • Hydrolysis of aqueous sucrose solution in the presence of a aqueous mineral acid
    • $$2{ H }_{ 2 }{ O }_{ 2 }\left( l \right) \underrightarrow { \quad \quad Pt\left( s \right) \quad \quad } 2{ H }_{ 2 }O\left( l \right) +{ O }_{ 2 }\left( g \right) $$
    • Hydrolysis of liquid in the presence of aqueous mineral acid
    Which of the following is NOT used in making photographic plates using colloidal sols?
    • Silver bromide
    • Gelatin
    • Glass plate
    • Argyrol
    In Bredig's Arc method,the stabilizer used is:
    • $$Ca(OH)_2$$
    • $$CaO$$
    • $$KOH$$
    • $$K_2O$$
    Collodion is a:
    • colloidal sol of cellulose nitrate in water
    • colloidal sol of cellulose acetate in ethyl alcohol
    • colloidal sol of cellulose nitrate in ethyl alcohol
    • colloidal sol of cellulose acetate in water
    Which of the following is NOT a condensation method?
    • solvent exchange method
    • physical state change method
    • peptization
    • chemical methods
    Which on adding to freshly precipitated aluminium hydroxide and shaking produces sol of aluminium hydroxide?
    • insufficient quantity of conc $$HCl$$
    • sufficient quantity of conc $$HCl$$
    • insufficient quantity of very dil $$HCl$$
    • sufficient quantity of very dil $$HCl$$
    The colour of the colloidal solution formed by combination of ferric chloride and freshly prepared ferric hydroxide is:
    • red
    • reddish-brown
    • green
    • grey
    Which of the following sol is not prepared using Bredig's arc method?
    • Silver sol
    • Copper sol
    • Gold sol
    • Platinum sol
    Peptization of silver iodide can take place on addition of: 
    • silver nitrate
    • potassium iodide
    • potassium nitrate
    • potassium chloride
    The peptizing agent used in Peptization is a/an:
    • stabilizer
    • electrolyte
    • proton donor
    • promoter
    The stabilizer used in the preparation of colloidal sol of mercury and sulphur is:
    • an ammonium salt
    • a citrate
    • $$KOH$$
    • both A and B
    The processes involved in Bredig's Arc method is/are:
    • dispersion
    • condensation
    • vapourisation
    • sublimation
    The sol used in eye lotion is:
    • silver solution
    • colloidal magnesium
    • colloidal gold
    • colloidal antimony
    The extent of adsorption of a gas on a solid depends on :
    • nature of the gas
    • pressure of the gas
    • temperature of the gas
    • all of the above
    Which of the following types of metals form the most efficient catalysts?
    • Alkali metals
    • Alkaline earth metals
    • Transition metals
    • All of the above
    Evaporation is the process which occurs:
    • from the bottom of the liquid
    • on the surface of the liquid
    • from the whole liquid on boiling
    • none of these
    A emulsifier is a substance which:
    • stabilises the emulsion
    • homogenises the emulsion
    • coagulates the emulsion
    • accelerates the dispersion of liquid in liquid
    Which of the following is an emulsifying agent?
    • Milk
    • Butter
    • Gum
    • Lamp black
    The process of separation of cream from milk is called:
    • emilsification
    • demulsification
    • electro-osmosis
    • peptization
    Milk is an emulsion in which:
    • a gas is dispersed in water
    • lactose is dispersed in water
    • milk fat is dispersed in water
    • a solid is dispersed in water
    Which of the following is an emulsifier?
    • Oil
    • Soap
    • Solvent
    • KCI
    A negatively charged suspension of clay in water will need for precipitation the minimum amount of:
    • aluminium chloride
    • potassium sulphate
    • sodium hydroxide
    • hydrochloric acid
    When freshly precipitated $$Fe{ \left( OH \right)  }_{ 3 }$$ is boiled with water in the presence of few drops of dil. $$HCl$$, a hydrated ferric oxide sol is obtained. This method is termed:
    • dialysis
    • peptization
    • ultrafiltration
    • electro-dispersion
    Sulphur sol contains:
    • discrete sulphur atoms
    • discrete sulphur molecules
    • water dispersed in solid sulphur
    • large aggregates of sulphur molecules
    Which of the following is not an example of a water-in-oil emulsion?
    • Cod liver oil
    •  Butter
    • Cold cream
    • Milk
    An emulsion is a colloidal solution consisting of:
    • two solids
    • two liquids
    • two gases
    • one solid and one liquid
    Emulsions of polyvinyl acetate are used in:
    • polishes
    • latex paints
    • fireworks
    • rayons
    Select the correct statement from the following.
    • Equilibrium constant changes with addition of a catalyst.
    • Catalyst increases the rate of forward reaction only.
    • The ratio of mixture at equilibrium does not change by catalyst.
    • Catalysts are active only in solution.
    When a sulphur sol is evaporated, solid sulphur is left. On mixing with water no colloidal sol is formed. The sulphur sol is:
    • hydrophilic
    • hydrophobic
    • reversible
    • lyophilic
    An emulsifier is a substance which:
    • stabilises the emulsion
    • homogenises the emulsion
    • coagulates the emulsion
    • accelerates the dispersion of liquid in liquid
    Which is not a colloidal solution of gas in liquid?
    • Froth
    • Foam with tiny bubbles
    • Mist
    • Whipped cream
    The emulsifying agent in milk is:
    • lactic acid
    • fat
    • lactose
    • casein
    Purple of cassius is:
    • colloidal solution of silver
    • colloidal solution of gold
    • colloid solution of platinum
    • oxy acids of gold
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