NCERT Class 12 Chemistry very short Questions & Answers
31 Which one of the following ore is concentrated by chemical leaching method?
A Argentite
B Cinnabar
C Copper pyrites
D Galena
32 In the following question a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
A Assertion and reason both are correct statements and reason is correct explanation for assertion.
B Assertion and reason both are incorrect statements.
C Assertion and reason both are correct statements but reason is not correct explanation for assertion.
D Assertion is correct statement but reason is wrong statement.
Answer: Assertion and reason both are incorrect statements.
33 Relative lowering of vapour pressure is a colligative property because ________ .
A It depends on the concentration of a non electrolyte solute in solution and does not depend on the nature of the solute molecules.
B It depends on the concentration of an electrolyte or nonelectrolyte solute in solution as well as on the nature of solute molecules.
C It depends on the concentration of a non electrolyte solute in solution as well as on the nature of the solute molecules.
D It depends on number of particles of electrolyte solute in solution and does not depend on the nature of the solute particles.
Answer: It depends on the concentration of a non electrolyte solute in solution and does not depend on the nature of the solute molecules.
34 Benzoic acid, when dissolved in benzene, which of the following is correct.
A The benzoic acid will undergo dissociation.
B The benzoic acid will undergo association.
C Observed molar mass of benzoic acid in benzene will less than normal molar mass.
D Observed molar mass of benzoic acid in benzene is more than normal molar mass.
Answer: The benzoic acid will undergo association.
35 In the commercial electrochemical process for aluminium extraction, electrolyte used is
A A molten mixture of Al2O3 and Na3AlF6.
B A molten mixture of Al2O3 and Al(OH)3.
C Al(OH)3 is NaOH solution.
D An aqueous solution of Al2 (SO4)3.
Answer: A molten mixture of Al2O3 and Na3AlF6.
36 Novolac, the linear polymer used in paints is
A copolymer of melamine and HCHO
B condensation polymer of phenol and HCHO
C copolymer of buta 1, 3-diene and styrene
D polymer of methyl methacrylate
Answer: condensation polymer of phenol and HCHO
37 The polymer containing strong intermolecular H-bonding and crystalline nature is
A Nylon 6, 6
B Teflon
C Polystyrene
D Natural rubber
38 Which ore can be best concentrated by froth floatation process?
A Galena
B Magnetite
C Malachite
D Cassiterite
39 3g of activated charcoal was added to 50 ml of acetic acid solution (0.06 M) in a flask. After an hour it was filtered and the strength of filtrate was found to be 0.042 M. The amount of acetic acid adsorbed per gram of charcoal is
A 42 mg
B 54 mg
C 36 mg
D 18 mg
40 During the adsorption of gas on the surface of solid, which of the following is true?
A ∆G 0, ∆S < 0
B ∆G > 0, ∆H < 0, ∆S < 0
C ∆G < 0, ∆H < 0, ∆S < 0
D ∆G < 0, ∆H 0
Answer: ∆G < 0, ∆H < 0, ∆S < 0
Question and Answers 