CBSE Chemistry Set- II Solved Question Paper 2012, given here.
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Some solved questions from CBSE Class 12th Chemistry Question Paper (Set-II) are given here
Q. what is meant by 'doping' in a semiconductor?
Answer. Doping: - It is adding appropriate amount of suitable impurities in the semiconductor
Q. what is the role of graphite in the electrometallurgy of aluminium?
Answer. Graphite is used as both anode as well as cathode. It prevents the formation of oxygen gas.
Q. Arrange the following compounds in an increasing order or their reactivity in nucleophilic addition reactions: ethanal, propanal, propanone, butanone.
Answer. Butanone, propanone, propanal, ethanol
Q. Define the term, ‘homopolymerisation’ giving an example.
Answer. Homopolymerisation: - It is a type of addition polymerisation in which polymerisation of a single monomeric species occurs. For example- formation of polythene from ethane
Q. What is meant by coagulation of a colloidal solution? Describe briefly any three methods by which coagulation of lyophobic sols can be carried out.
Answer. Coagulation of a colloidal solution: - It is the process of settling of colloidal particles.
Methods by which coagulation of lyophobic sols can be carried out are described as follows:
a. Electrophoresis: - In the presence of oppositely charged electrodes, the colloidal particles starts moving towards them, get discharged and precipitated under an applied electric field.
b. Persistent dialysis: - On prolonged dialysis, traces or the electrolyte present in the sol are removed almost completely and the colloids become unstable and ultimately coagulate.
c. Boiling: - when a sol is boiled, the adsorbed layer is disturbed due to increased collisions with the molecules of dispersion medium. This reduces the charge on the particles and ultimately led to settling down in the form of precipitate.
Q. Describe the principle involved in each of the following processes.
(i) Mond process for refining of Nickel.
(ii) Column chromatography for purification of rare elements.
Answer. Principle of mond process: - in this method, the metal is converted into its volatile compound & collected elsewhere. After that it is decomposed to give pure metal.
Column chromatography: - in this method, different components of a mixture are differently absorbed on an adsorbent.
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