Chemistry:2009:CBSE:[Delhi]:Set-I
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Q1
Which point defect in crystals does not alter the density of the relevant solid?
Marks:1View AnswerAnswer:
Frenkel defect is the point defect, which does not alter the density of relevant solid.
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Q2
Define the term ‘Tyndall effect’.
Marks:1View AnswerAnswer:
Tyndall effect is scattering of light by colloidal solutions. When a beam of visible light passes through colloidal solution, it is scattered and the path of beam is illuminated.
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Q3
Why is the froth flotation method selected for the concentration of Sulphide ores ?
Marks:1View AnswerAnswer:
Sulphide ores are concentrated by froth flotation method because particles of sulphide ore are hydrophobic and they become wet by oil while gangue particles are wetted by water.
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Q4
Why is Bi(V) a stronger oxidant than Sb (V) ?
Marks:1View AnswerAnswer:
Oxidising agent is the substance, which accepts electron/s. Since Bi (V) can accept electrons easily as compared to Sb (V), it is better oxidising agent than Sb (V).
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Q5
Give the IUPAC name of the following compound:
Marks:1View AnswerAnswer:
2- bromo 3-methyl but-2 en-1-ol
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Q6
White the structure of 3-oxopentanal.
Marks:1View AnswerAnswer:
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Q7
Why is an alkylamine more basic than ammonia ?
Marks:1View AnswerAnswer:
Electron donors are bases. Alkyl group is electron donor. Ammonia does not have any alkyl group whereas alkyl amines have alkyl group. Since electron donor groups increase the basicity, alkyl halides are more basic than ammonia.
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Q8
Give an example of elastomers.
Marks:1View AnswerAnswer:
Buna –N is an example of elastomer.
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Q9
A reaction is of second order with respect to a reactant. How will the rate of reaction be affected if the concentration of this reactant is
(i) doubled,
(ii) reduced to half?Marks:2View AnswerAnswer:
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Q10
Explain the role of
(i)Cryolite in the electrolytic reduction of alumina.
(ii)Carbon monoxide in the purification of nickel.Marks:2View AnswerAnswer:
(i) Cryolite is added during reduction of alumina to lower its temperature and increase its conductivity.
(ii) In purification of nickel, carbon monoxide is added with impure nickel to form volatile nickel tetracarbonyl, which decomposes at high temperature to form pure nickel.
