Class 12 Chemistry - Chapter General Principles and Processes of Isolation of Elements NCERT Solutions | Explain: (i) Zone refining
Explain: (i) Zone refining (ii) Column chromatography.
(i) Zone refining: This method is based on the principle that impurities are more soluble in the molten state of metal than in the solid state. In the process of zone refining, a circular mobile heater is fixed at one end of a rod of impure metal. As the heater moves, the molten zone of the rod also moves with it. As a result, pure metal crystallizes out of the melt and the impurities pass onto the adjacent molten zone. This process is repeated several times, which leads to the segregation of impurities at one end of the rod. The end with the impurities is cut off. Silicon, boron, gallium, indium etc. can be purified by this process.
(ii) Column chromatography: Column chromatography is a technique used to separate different components of a mixture. It is a very useful technique used for the purification of elements available in minute quantities. It is also used to remove the impurities that are not very different in chemical properties from the element to be purified. Chromatography is based on the principle that different components of a mixture are differently adsorbed on an adsorbent. In chromatography, there are two phases: mobile phase and stationary phase. The stationary phase is immobile and immiscible. Al2O3 column is usually used as the stationary phase in column chromatography. The mobile phase may be a gas, liquid, or supercritical fluid in which the sample extract is dissolved. Then, the mobile phase is forced to move through the stationary phase. The component that is more strongly adsorbed on the column takes a longer time to travel through it than the component that is weakly adsorbed. The adsorbed components are then removed (eluted) using a suitable solvent (eluant).
More Questions From Class 12 Chemistry - Chapter General Principles and Processes of Isolation of Elements
- Q:-
What is the significance of leaching in the extraction of aluminium?
- Q:-
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
- Q:-
Copper can be extracted by hydrometallurgy but not zinc. Explain.
- Q:-
Outline the principles of refining of metals by the following methods:
(i) Zone refining
(ii) Electrolytic refining
(iii) Vapour phase refining
- Q:-
Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present ?
- Q:-
The reaction,
Cr2O3 + 2Al → Al2O3 + 2Cr (ΔGo = -421kJ)
is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?
- Q:-
How can you separate alumina from silica in bauxite ore associated with silica? Give equations, if any.
- Q:-
Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?
- Q:-
Write chemical reactions taking place in the extraction of zinc from zinc blende.
- Q:-
Describe a method for refining nickel.
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 any two characteristics of Chemisorption.
- 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:-
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:-
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
- Q:-
Arrange the following metals in the order in which they displace each other from the solution of their salts.
Al, Cu, Fe, Mg and Zn
- Q:-
The molar conductivity of 0.025 mol L-1 methanoic acid is
46.1 S cm2 mol-1.
Calculate its degree of dissociation and dissociation constant. Given λ0(H+)
= 349.6 S cm2 mol-1 and λ0(HCOO-) = 54.6 S cm2 mol
- Q:-
Boiling point of water at 750 mm Hg is 99.63°C. How much sucrose is to be added to 500 g of water such that it boils at 100°C.Molal elevation constant for water is 0.52 K kg mol-1.
- Q:-
Give the uses of freon 12, DDT, carbon tetrachloride and iodoform.
- Q:-
What modification can you suggest in the Hardy-Schulze law?
- Q:-
What is an adsorption isotherm? Describe Freundlich adsorption isotherm.
- Q:-
The oxidation number of cobalt in K[Co(CO)4] is
(i) +1
(ii) +3
(iii) -1
(iv) -3
- Q:-
Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 125 pm.
(i) What is the length of the side of the unit cell?
(ii) How many unit cells are there in 1.00 cm3of aluminium?
- Q:-
What are the factors which influence the adsorption of a gas on a solid?
2 Comment(s) on this Question
Best answer
Write short note on zone refining
- All Chapters Of Class 12 Chemistry
- All Subjects Of Class 12