Class 12 Chemistry - Chapter Surface Chemistry NCERT Solutions | What role does adsorption play in hetero
What role does adsorption play in heterogeneous catalysis?
The phenomenon of concentration of molecules of a gas or liquid at a solid surface is called adsorption.
Heterogenous catalysis is a catalysis in which the catalyst is in different physical phase from the reactant. The most important of such reactions are those in which the reactants are in the gas phase while the catalyst is a solid.
This heterogeneous catalytic action can be explained in terms of the adsorption theory. The mechanism of catalysis involves the following steps:
(i) Adsorption of reactant molecules on the catalyst surface.
(ii) Occurrence of a chemical reaction through the formation of an intermediate.
(iii) De-sorption of products from the catalyst surface.
(iv) Diffusion of products away from the catalyst surface.
(v) Diffusion of reactants to the surface of the catalyst.
The reaction occurs by the contact of reactants with the catalyst surface.The molecule of reactant (gas) are adsorbed at the catalyst surface where they form an ‘adsorption complex’. The catalyst surface behave like the surface molecules of a liquid and are not surrounded by atoms or molecules of their kind. Therefore, they have unbalanced or residual attractive forces (Vander waal’s forces) on the surface which can hold adsorbate particles.As the concentration of reactants on the surface of the catalyst increases, the rate of reaction also increases. In such reactions, the products have very less affinity for the catalyst and are quickly desorbed, thereby making the surface free for other reactants.
More Questions From Class 12 Chemistry - Chapter Surface Chemistry
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Explain what is observed
(i) When a beam of light is passed through a colloidal sol.
(ii) An electrolyte, NaCl is added to hydrated ferric oxide sol.
(iii) Electric current is passed through a colloidal sol?
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Why is adsorption always exothermic?
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(i) Electrophoresis
(ii) Coagulation
(iii) Dialysis
(iv) Tyndall effect.
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Explain the terms with suitable examples:
(i) Alcosol
(ii) Aerosol
(iii) Hydrosol
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(i) Physical states of components
(ii) Nature of dispersion medium and
(iii) Interaction between dispersed phase and dispersion medium?
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Popular Questions of Class 12 Chemistry
- Q:-
For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.
- Q:-
Write the formulas for the following coordination compounds:
(i) Tetraamminediaquacobalt (III) chloride
(ii) Potassium tetracyanonickelate(II)
(iii) Tris(ethane-1,2-diamine) chromium(III) chloride
(iv) Amminebromidochloridonitrito-N-platinate(II)
(v) Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate
(vi) Iron(III) hexacyanoferrate(II)
- Q:-
(i) Write structures of different isomeric amines corresponding to the molecular formula, C4H11N
(ii) Write IUPAC names of all the isomers.
(iii) What type of isomerism is exhibited by different pairs of amines?
- Q:-
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- Q:-
Write the structures of the following compounds.
(i) α-Methoxypropionaldehyde
(ii) 3-Hydroxybutanal
(iii) 2-Hydroxycyclopentane carbaldehyde
(iv) 4-Oxopentanal
(v) Di-sec-butyl ketone
(vi) 4-Fluoroacetophenone
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Which of the ores mentioned in Table 6.1 can be concentrated by magnetic separation method?
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Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?
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Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water. Explain.
- Q:-
Write structures of the following compounds:
(i) 2-Chloro-3-methylpentane
(ii) 1-Chloro-4-ethylcyclohexane
(iii) 4-tert. Butyl-3-iodoheptane
(iv) 1,4-Dibromobut-2-ene
(v) 1-Bromo-4-sec. butyl-2-methylbenzene
Recently Viewed Questions of Class 12 Chemistry
- Q:-
How the following conversions can be carried out?
(i) Propene to propan-1-ol
(ii) Ethanol to but-1-yne
(iii) 1-Bromopropane to 2-bromopropane
(iv) Toluene to benzyl alcohol
(v) Benzene to 4-bromonitrobenzene
(vi) Benzyl alcohol to 2-phenylethanoic acid
(vii) Ethanol to propanenitrile
(viii) Aniline to chlorobenzene
(ix) 2-Chlorobutane to 3, 4-dimethylhexane
(x) 2-Methyl-1-propene to 2-chloro-2-methylpropane
(xi) Ethyl chloride to propanoic acid
(xii) But-1-ene to n-butyliodide
(xiii) 2-Chloropropane to 1-propanol
(xiv) Isopropyl alcohol to iodoform
(xv) Chlorobenzene to p-nitrophenol
(xvi) 2-Bromopropane to 1-bromopropane
(xvii) Chloroethane to butane
(xviii) Benzene to diphenyl
(xix) tert-Butyl bromide to isobutyl bromide
(xx) Aniline to phenylisocyanide
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Write the formulas for the following coordination compounds:
(i) Tetraamminediaquacobalt (III) chloride
(ii) Potassium tetracyanonickelate(II)
(iii) Tris(ethane-1,2-diamine) chromium(III) chloride
(iv) Amminebromidochloridonitrito-N-platinate(II)
(v) Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate
(vi) Iron(III) hexacyanoferrate(II)
- Q:-
The Eθ(M2+/M) value for copper is positive (+0.34V). What is possibly the reason for this? (Hint: consider its high ΔaHV and low ΔhydHV)
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What happens when sulphur dioxide is passed through an aqueous solution of Fe(III) salt?
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Arrange each set of compounds in order of increasing boiling points.
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(ii) 1-Chloropropane, Isopropyl chloride, 1-Chlorobutane.
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Write a balanced equation for the hydrolytic reaction of PCl5 in heavy water.
- Q:-
The rate constant for the decomposition of N2O5 at various temperatures is given below:
T/°C
0 20 40 60 80 105 X K /S-1
0.0787 1.70 25.7 178 2140 Draw a graph between ln k and 1/T and calculate the values of A and Ea.
Predict the rate constant at 30 º and 50 ºC.
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Calculate the standard cell potentials of galvanic cells in which the following reactions take place:
(i) 2Cr(s) + 3Cd2+(aq) → 2Cr3+(aq) + 3Cd
(ii) Fe2+(aq) + Ag+(aq) → Fe3+(aq) + Ag(s)
Calculate the ΔrGø¸ and equilibrium constant of the reactions.
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The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 Scm-1. Calculate its molar conductivity.
- Q:-
The cell in which the following reactions occurs:
has Eøcell = 0.236 V at 298 K.
Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.
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