CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 11 - MCQExams.com

Consider the following reactions at 300 K: X $$\rightarrow$$ Y (uncatalysed reaction) & X $$\rightarrow$$ Y (catalysed reaction). The energy of activation is lowered by 83.14 kJmol$$^{-1}$$ for the catalysed reaction. 
The rate of catalysed reaction is:
  • $$3\times 10^{14}$$ times that of uncatalysed reaction
  • $$15\times 10^{14}$$ times that of uncatalysed reaction
  • 25 times that of uncatalysed reaction
  • 22 times that of uncatalysed reaction
A reaction is catalysed by $$H^{+}$$ ion in the presence of $$HA$$, rate constant is $$2\times 10^{-3}min^{-1}$$ and in presence of $$HB$$, rate constant is $$1\times 10^{-3}min^{-1}$$ . $$HA$$ and $$HB$$ (both strong acids) have relative strength as:
  • $$0.5$$
  • $$0.002$$
  • $$0.001$$
  • $$2$$
Methylene blue is adsorbed on activated charcoal at $$25^{0}C$$ from its aqueous solution. Which is the correct statement for this process?
  • The adsorption requires activation at $$25^{0}C$$.
  • The adsorption is accompanied by a decrease in enthalpy.
  • The adsorption increases with increase of temperature.
  • The adsorption is irreversible.
Which of the following are the correct statements regarding the catalyzed and uncatalyzed reactions at constant temperature?
  • Catalyzed reaction does not alter $$\Delta H$$ of the reaction
  • At constant temperature, $$\Delta G^0$$ of the catalysed and uncatalyzed reaction is same
  • Catalyzed reaction alters equilibrium constant even at constant temperature
  • Catalysed reaction alters $$r_f$$ and $$r_b$$ values equally at constant temperature
A reaction is catalysed by $$H^+ $$ ion. In presence of HA, rate constant is $$2\times 10^{-3} min^{-1}$$ and in presence of HB rate constant is $$1\times 10^{-3} min^{-1}$$, HA and HB both being strong acids, we may conclude that:
  • equilibrium constant is 2.
  • HA is stronger acid than HB.
  • relative acidic strength of HA and HB is 2.
  • HA is weaker acid than HB and relative strength is 0.5.
Assertion: A negative catalyst retards the rate of chemical reaction.
Reason: Presence of negative catalyst boosted up the energy of activation.
  • Assertion is correct but Reason is wrong
  • Assertion is wrong but Reason is correct
  • Both Assertion and explanation are correct and Reason is correct explanation of Assertion
  • Both Assertion and explanation are correct but Reason is not correct explanation of Assertion
The solution of $$H_2O_2$$ can be stored for a long time at room temperature. However, bubbles of oxygen form as soon as a drop of bromine is added. The role of bromine for the reaction $$2H_2O_2(aq)\rightarrow 2H_2O(l)+O_2(g)$$ is :
  • to act as a positive catalyst
  • to form an intermediate $$(Br^-)$$ on reacting with $$H_2O_2$$ following reduction of bromine and then to show oxidation of $$Br^{-}$$ to $$Br_2$$ by $$H_2O_2$$
  • to act as heterogeneous catalyst
  • to act as negative catalyst
Which acts as a negative catalyst?
  • Lead tetraethyl as antiknock compound.
  • Glycerol in decomposition of $$H_2O_2$$.
  • Ethanol in oxidation of chloroform.
  • None of the above.
Consider the following statements and arrange in the order of true/false as given in the codes.
$$S_1: $$ The rate of the reaction A $$\rightarrow$$ B having the rate law $$- \displaystyle \frac{d[A]}{dt} = k [A] [B]$$ when plotted against time will exhibit a maximum at some time.
$$S_2: $$ A catalyst in a chemical reaction increases the forward E$$_a$$ and decreases the backward $$E_a$$.
$$S_3: $$ A catalyst in a chemical reaction decreases both forward and backward $$E_a$$.
$$S_4: $$ For a first-order reaction, the time required to reduce successively the concentration of reactant by a constant fraction is always same.
  • TTTT
  • FFFF
  • FTFT
  • TFTT
Select the incorrect statement regarding the given reaction.

$$RCOCl+H_2\xrightarrow{Pd-BaSO_4} RCHO+HCl$$
  • $$Pd$$ acts as a positive catalyst.
  • It is Rosenmund reaction.
  • $$BaSO_4$$ acts as poison for $$Pd$$.
  • $$BaSO_4$$ acts as promoter for $$Pd$$.
Identify the true statement(s):
  • A catalyst is chemically unchanged at the end of a reaction
  • A catalyst may appear in the kinetic rate equation of the reaction
  • A catalyst will not affect the composition of an equilibrium mixture
  • A catalyst cannot cause a non-spontaneous ($$\Delta$$ G > 0) reaction to proceed
The catalyst provides a new pathway involving lower amount of activation energy, to make the reaction fast. Which of the following is/are the result of catalytic action?
  • Catalyst decreases $$E_a/RT$$ value.
  • Catalyst increases $$-E_a/RT$$ value.
  • Catalyst increases $$e^{E_a/RT}$$ value.
  • Catalyst increases k of reaction.
Which is wrong about a positive catalyst?
  • It lowers the energy of activation of forward reaction
  • It lowers the threshold energy level
  • It lowers the energy of activation of backward reaction
  • It makes the reaction more exothermic or endothermic
Identify an emulsion from among the following.
  • Ruby
  • Sponge
  • Milk
  • Jellies
Which of the following cannot be used to prepare an emulsion of benzene in water?
  • $$CH_3-(CH_2)_9-(SO_3)^-Na^+$$
  • $$CH_3-(CH_2)_9-COO^-Na^+$$
  • $$CH_3-(CH_2)_9-NH_3^+Cl^-$$
  • $$(CH_3)_4 \overset{+}{N}Br^-$$
Which of the following statements about physical adsorption is not correct?
  • It is usually monolayer
  • It is reversible in nature
  • It involves van der Waals interactions between adsorbent and adsorbate
  • It involves small value of adsorption
Colloidal gold can be prepared by:
  • bredig's arc method
  • reduction of $$\displaystyle AuCl_{3}$$
  • hydrolysis
  • peptization
Which of the following graphs shows the variation of physical adsorption with temperature?
Consider the following sequence of reactions:

Red Hot Coke$$\ +\ $$Steam $$\xrightarrow {\displaystyle \text{Y}{(\text{catalyst})}} X \longrightarrow Z  \xrightarrow [\displaystyle \text{cold water}]{\displaystyle \text{pressure}}\ $$W(gas)

$$\text{Y}$$ is:
  • $$V_{2}O_{5}$$
  • $$Pt$$
  • $$Fe_{2}O_{3}/Cr_{2}O_{3}$$
  • $$Ni$$
Smoke screens consist of:
  • fine particles of $$TiO_2$$ dispersed in air by aeroplanes
  • fine particles of $$AgI$$ dispersed in air by aeroplanes
  • fine particles of $$Al_2O_3$$ dispersed in air by aeroplanes
  • none of the above
Which of the following statements is/are true for physisorption?
  • Extent of adsorption increases with increase in pressure.
  • It needs activation energy.
  • It can be reversed easily.
  • It occurs at high temperature.
Which of the following is not correct for heterogeneous catalysis?
  • The catalyst decreases the energy of activation
  • The surface of catalyst plays an important role
  • The catalyst actually forms a compound with reactants
  • There is no change in the energy of activation
Which statement is incorrect?
  • Catalytic decomposition of $$KClO_3$$ by $$MnO_2$$ is an example of homogeneous catalysis.
  • Only the surface atoms in an adsorbent play an active role in adsorption.
  • The rate of adsorption is very rapid in the beginning but decreases gradually until equilibrium is attained.
  • Absorption proceeds at a steady rate.
How many $$N{H}_{3}$$ molecules are adsorbed on charcoal surface?
  • $$1.4\times {10}^{22}$$
  • $$1.4\times {10}^{23}$$
  • $$1.4\times {10}^{21}$$
  • $$1.4\times {10}^{20}$$
Which characteristic is not correct for physical adsorption?
  • Adsorption is spontaneous.
  • Both enthalpy and entropy change of adsorption are negative.
  • Adsorption on solid is reversible.
  • Adsorption increases with increase in temperature.
Select the wrong statement.
  • The reducing power of $$H_2$$ is increased if it is absorbed on $$Pd$$.
  • Thermite welding does not require a catalyst.
  • The decomposition of $$H_2O_2(l)$$ in presence of $$Hg(l)$$ is homogeneous catalysis.
  • The chemical adsorption requires activation energy.
Methylene blue is adsorbed on activated charcoal at $$25^oC$$ from its aqueous solution. For this process, select the correct statement.
  • The adsorption requires activation at $$25^oC$$
  • The adsorption is accompanied by a decrease in enthalpy
  • The adsorption increases with increase of temperature
  • The adsorption is irreversible
Which statements are correct?
Addition of $$AgNO_3$$ drop by drop in excess of $$KI$$ leads to the formation of $$+$$vely charged sol of $$AgI$$.
Adsorption characteristic of an adsorbent may be increased by making it in finely divided form.
Catalyst help in attaining the equilibrium earlier but does not influence equilibrium constant in reversible reactions.
Decolorisation of raw sugar is based on absorption.
Gas masks containing animal charcoal acts on the basis of selective adsorption.
The micelle formation of soaps depends upon hydrophobic and hydrophilic entities present in soap.
  • $$2,\: 3,\: 5,\: 6$$
  • $$2,\: 3,\: 4,\: 5$$
  • $$1,\: 2,\: 5,\: 6$$
  • $$1, \:2, \:3, \:4$$
Mention catalyst in the following reaction:
$$CS_2+3Cl_2 \rightarrow  CCl_4 + S_2Cl_2$$ 
  • $$MnO_2$$
  • $$FeCl_3$$
  • $$PdCl_2$$
  • $$ZnO/CuO$$
One gram of charcoal adsorbs $$400$$ mL of $$0.5\ M$$ acetic acid to form a monolayer, and the molarity of acetic acid reduces to $$0.49\ M$$. Calculate the surface area of charcoal adsorbed by each molecule of acetic acid, where the surface area of charcoal is $$3.01\times 10^{2}$$ m$$^{2}$$ g$$^{-1}$$.
  • $$1\times 10^{-19}m^{2}$$
  • $$1.2\times 10^{-19}m^{2}$$
  • $$2.5\times 10^{-21}m^{2}$$
  • None of these
Which of the following statements is incorrect regarding physisorption?
  • It occurs because of van der Waals forces
  • Liquefiable gases are adsorbed more easily
  • Enthalpy of adsorption $$(\Delta H_{adsorption})$$ is high and negative
  • Enthalpy of adsorption $$(\Delta H_{adsorption})$$ is low and positive
When dilute aqueous solution of $$AgNO_3$$ (excess) is added to $$KI$$ solution, positively charged sol particles of $$AgI$$ are formed due to adsorption of ion :
  • $$K^+$$
  • $$Ag^+$$
  • $$I^-$$
  • $$NO_3^-$$
Select incorrect statement(s):
  • Surface active agent like soaps and synthetic detergents are micelles.
  • Soaps are emulsifying agents.
  • $$C_{17}H_{35}$$ (hydrocarbon part) and COO (carboxylate part) of stearate ion $$(C_{17}H_{35}COO^-)$$ are both hydrophobic.
  • The hydrophobic part accumulates inside of the micelle when soap is mixed in water.
Select the correct statements about preparation of colloidal solution.
  • Various substances such as mercury, oil, sulphur etc. are passed in colloidal state by using ultrasonic vibrations.
  • A precipitate of $$BaSO_4$$ can be passed in colloidal state by continuous washing with water.
  • A solution of indigo in suitable solvent is added drop by drop to water forms a colloidal solution of indigo in water.
  • Peptisation is a characteristic property of colloidal state.
Oil soluble dye is mixed with water in oil emulsion, then:
  • dispersion medium is coloured
  • dispersed phase is coloured
  • both are coloured
  • none is coloured
Preparation of Lyophobic sols by chemical method involves :
  • double decomposition
  • oxidation and reduction
  • hydrolysis
  • all of these
A soap $$(C_{17}H_{35} COONa)$$ solution becomes a colloidal sol at a concentration of $$1.2\times 10^{3} M$$. On the average, $$2.4\times 10^{13}$$ colloidal particles are present in $$1 mm^3$$. What is the average number of stearate ions (in multiples of $$10^6$$) in one colloidal particle (micelle)?
  • 30
  • 40
  • 50
  • 60
Which of the following are cation exchange resin and anion exchange resins?
  • $$NH_4OH$$ , $$RCHO$$
  • $$RNH_3OH$$ , $$RCOOH$$ or $$RSO_3H$$
  • $$RNH_3Cl$$ , $$RSO_4H$$
  • None of these
$$3$$ g of activated charcoal was added to $$50$$ mL of the acetic acid solution $$(0.06\ N)$$ in a flask. After an hour, it was filtered and the strength of the filtrate was found to be $$0.042\ N$$. The amount of acetic acid adsorbed (per gram of charcoal) is :
  • $$18$$ mg
  • $$36$$ mg
  • $$42$$ mg
  • $$54$$ mg
Match the List I with List II and choose the correct option from the codes given below:
List - IList - II
(P)Peptisation(1)Sky in blue
(Q)Delta Formation(2)Gold number
(R)Tyndall effect(3)Coagulation
(S)Protection power of colloids(4)Adsorption of common ion
  • P-3, Q-4, R-1, S-2
  • P-2, Q-3, R-1, S-4
  • P-3, Q-1, R-4, S-2
  • P-4, Q-3, R-1, S-2
The qualitative sketches I, II and III given below show the variation of surface tension with molar concentration of three different aqueous solutions of $$KCl, CH_{3}OH$$ and $$CH_{3}(CH_{2})_{11}OSO_{3}^{-} Na^{+}$$ at room temperature.

The correct assignment of the sketches is:

478168.png
  • $$I: KCl; II: CH_{3}OH; III: CH_{3}(CH_{2})_{11}OSO^{-}_{3}Na^{+}$$
  • $$I: CH_{3}(CH_{2})_{11}OSO^{-}_{3}Na^{+} II: CH_{3}OH; III: KCl$$
  • $$I: KCl; II: CH_{3}(CH_{2})_{11}OSO^{-}_{3}Na^{+}; III: CH_{3}OH$$
  • $$I: CH_{3}OH; II: KCl; III: CH_{3}(CH_{2})_{11}OSO^{-}_{3}Na^{+}$$
A student takes about 4 ml of distilled water in four test tubes marked $$P, Q, R$$ and $$S$$. He then dissolves in each test tube, an equal amount of various salts, viz. sodium sulphate in $$P$$, potassium sulphate in $$Q$$, calcium sulphate in $$R$$ and magnesium sulphate in $$S$$. After that, he adds an equal amount of soap solution in each test tube. On shaking each of these test tubes well, he observes a good amount of lather (foam) in the test tube marked:
  • $$P$$ and $$Q$$
  • $$Q$$ and $$R$$
  • $$P, Q$$ and $$S$$
  • $$P, R$$ and $$S$$
Foam is formed when_______
  • A solid dispersed in a liquid
  • A liquid dispersed in a liquid
  • A gas dispersed in a liquid
  • A liquid dispersed in a gas
Pick out the statement which is not relevant in the discussion of colloids:
  • sodium aluminium silicate is used in the softening of hard water
  • potash alum is used in shaving rounds and as a styptic in medicine
  • artificial rain is caused by throwing electrified sand on the clouds from an aeroplane
  • deltas are formed at a place when the river pours its water into the sea
Physisorption is :
  • It is highly specific in nature
  • It is reverisible
  • It is caused by chemical bond formation
  • All of the above
Which of the following option is correct for colloids?
  • Blue color of the sky is due to the scattering of light by colloidal dust particles in air
  • Sea water looks blue due to scattering of light by the colloidal impurities present in sea water.
  • Blood is a colloidal solution
  • All of the above
Smoke particles are actually electrically charged colloidal particles of :
  • carbon in air
  • water droplets in air
  • sulphur in air
  • titanium oxide in air
The colloidal solution of $$X$$ in gelatin is applied in glass plates to form sensitive plates in photography. Identify $$X$$:
  • Silver chloride
  • Silver bromide
  • Sodium chloride
  • Sodium bromide
Which of the following is absorbed efficiently in colloidal forms?
  • Colloidal sulphur
  • Colloidal gold
  • Colloidal copper
  • Colloidal mercury
Soap solution is colloidal in nature and remove the dust particles by which of the following process?
  • Emulsification
  • Adsorbtion
  • Stripping
  • Distillation
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 12 Engineering Chemistry Quiz Questions and Answers