Class 12 Chemistry - Chapter Surface Chemistry NCERT Solutions | What are lyophilic and lyophobic sols? G
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
Sols are colloidal systems in which a solid is dispersed in a liquid. They are of two types:
(i) Lyophilic sols (solvent loving):
They are those in which the dispersed phase exhibits a definite affinity for the dispersion medium (liquid) or the solvent. For example: Dispersion of starch, gum & protein in water. The affinity of sol particles for the medium is due to hydrogen bonding with water (dispersion medium). They may have little or no charge at all & they donot exhibit Tyndall effect. These sols are reversible in nature i.e., if two constituents of the sol are separated by any means (such as evaporation), then the sol can be prepared again by simply mixing the dispersion medium with the dispersion phase and shaking the mixture.
(ii) Lyophobic sols:
They are those in which the dispersed phase has no attraction for the dispersion medium or the solvent. For example: Dispersion of gold, iron & sulphur in water. Their colloidal sols can be prepared only by special methods. The particles carry positive or negative charge& they do exhibit Tyndall effect. These sols are irreversible in nature.
Now, the stability of a lyophobic sol is due to the adsorption of positive or negative ions by the dispersed particles. The repulsive forces between the charged particles donot allow them to settle.If some how ,the charge is removed, there is nothing to keep the particles apart from each other. They aggregate or flocculate & settle down under the action of gravity. In lyophobic sols,they are not surrounded by adsorbed layer of dispersion medium, as a result they come together & coagulate. So whenever an excess of electrolyte is added or boiling is done, the electrolyte furnishes both positive & negative ions in the medium & the sol particles adsorb oppositely charged ions & gets discharged. The electrically neutral particles then aggregate & settle down as precipitate. The stability of hydrophilic sols depends on two things- the presence of a charge and the salvation of colloidal particles. On the other hand, the stability of hydrophobic sols is only because of the presence of a charge. Therefore, the latter are much less stable than the former.
More Questions From Class 12 Chemistry - Chapter Surface Chemistry
- Q:-
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?
- Q:-
Why is adsorption always exothermic?
- Q:-
What do you mean by activity and selectivity of catalysts?
- Q:-
What modification can you suggest in the Hardy-Schulze law?
- Q:-
Explain the following terms:
(i) Electrophoresis
(ii) Coagulation
(iii) Dialysis
(iv) Tyndall effect.
- Q:-
What is an adsorption isotherm? Describe Freundlich adsorption isotherm.
- Q:-
Explain the terms with suitable examples:
(i) Alcosol
(ii) Aerosol
(iii) Hydrosol
- Q:-
How are colloids classified on the basis of
(i) Physical states of components
(ii) Nature of dispersion medium and
(iii) Interaction between dispersed phase and dispersion medium?
- Q:-
Discuss the effect of pressure and temperature on the adsorption of gases on solids.
- Q:-
Why does physisorption decrease with the increase of temperature
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:-
Why are solids rigid?
- 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
- Q:-
Which of the ores mentioned in Table 6.1 can be concentrated by magnetic separation method?
- Q:-
Why are pentahalides more covalent than trihalides?
- Q:-
Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?
- Q:-
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:-
Calculate the mass of ascorbic acid (Vitamin C, C6H8O6) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5°C. Kf= 3.9 K kg mol-1.
- Q:-
Identify the monomer in the following polymeric structures.
(i)
(ii)
- Q:-
H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry's law constant.
- Q:-
(i) Draw the structures of all isomeric alcohols of molecular formula C5H12O and give their IUPAC names.
(ii) Classify the isomers of alcohols in question 11.3 (i) as primary, secondary and tertiary alcohols.
- Q:-
Give simple chemical tests to distinguish between the following pairs of compounds.
(i) Propanal and Propanone
(ii) Acetophenone and Benzophenone
(iii) Phenol and Benzoic acid
(iv) Benzoic acid and Ethyl benzoate
(v) Pentan-2-one and Pentan-3-one
(vi) Benzaldehyde and Acetophenone
(vii) Ethanal and Propanal
- Q:-
How are the following conversions carried out?
(i) Propene → Propan-2-ol
(ii) Benzyl chloride → Benzyl alcohol
(iii) Ethyl magnesium chloride → Propan-1-ol.
(iv) Methyl magnesium bromide → 2-Methylpropan-2-ol.
- Q:-
Write the conditions to maximize the yield of H2SO4 by Contact process.
- Q:-
Draw the structures of the following compounds.
(i) 3-Methylbutanal (ii) p-Nitropropiophenone
(iii) p-Methylbenzaldehyde (iv) 4-Methylpent-3-en-2-one
(v) 4-Chloropentan-2-one (vi) 3-Bromo-4-phenylpentanoic acid
(vii) p,p'-Dihydroxybenzophenone (viii) Hex-2-en-4-ynoic acid
- Q:-
Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:
(i) Fe3+(aq) and I-(aq)
(ii) Ag+ (aq) and Cu(s)
(iii) Fe3+ (aq) and Br- (aq)
(iv) Ag(s) and Fe3+ (aq)
(v) Br2 (aq) and Fe2+ (aq).
- Q:-
How would you determine the standard electrode potential of the system Mg2+ | Mg?
6 Comment(s) on this Question
Not having comfortable language
Quite lengthy Not fine
Quite lengthy Not fine
Hi
Very poor
Very good
- All Chapters Of Class 12 Chemistry
- All Subjects Of Class 12