cbse 12th chemistry unsolved overall important question
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CBSE 12th Chemistry
Unsolved Overall Important Question Paper - III
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CBSE 12th Chemistry
Unsolved Overall Important Question Paper - III
Q.1. What is meant by βshape selective catalysisβ
Q.2. Five the IUPAC name of the following compound.
πΆπ»2 = πΆ β πΆπ»2π΅π | πΆπ»3
Q.3. Write the stricture to 3-oxpentanal.
Q.4. How many atoms constitute one-unit cell of a face-centered cubic crystal?
Q.5. Write IUPAC name of the following compound:
(ππππππ)πππππ
Q.6. State Raoultβs law for solutions, of volatile liquid components taking a suitable
example, explain the meaning of positive deviation from Raoultβs law.
OR
Define the term βosmotic pressureβ. Describe how the molecular mass of a substance
can be determined on the basis of osmotic pressure measurement.
Q.7. Which of the two components of starch is water soluble?
Q.8. An element with density π. π π ππβπ forms a π. π. π. unit cell with edge length
π Γ ππβπππ. Calculate the molar mass of the element.
(Given: π΅π¨ = π. πππ Γ πππππππβπ)
Q. 9. Draw the structures of the following molecules:
(i) πΏππΆππ (ii) π―ππ·πΆπ .
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Q.10. What type of cell is a lead storage battery? Write the anode and the cathode
reactions and the overall cell reaction occurring in the use of a lead storage?
Q.11. Silver crystallizes in face-center cubic unit cell. Each side of this unit cell has a
length of 400 pm. Calculate the radius of the silver. (Assume the atoms just touch
each other on the diagonal across the face of the unit cell. That is each face atom is
touching the four corner atoms.)
Q.12. Explain the mechanism of the following reaction:
Q.13. (a) What metal in the first transition series (3d series) exhibits + 1 oxidation state
most frequently and why?
(b) Which of the following cations are colored in aqueous solutions and why?
πΊπͺπ+, π½π+, π»ππ+,π΄ππ+(ππ. π§π¨π¬. ππ = ππ, π = ππ, ππ’ = ππ, ππ§ = ππ)
Q. 14. Write the principle of the following:
(a) Zone refining
(b) Froth floatation process
(c) Chromatography
Q. 15. Give the preparation and use of PVC (Polyvinyl Chloride)
Q.16. A first order reaction has a rate constant of π. ππππ πππβπ. If we begin with 0.10 M
concentration of the reactant, what concentration of reactant will remain in solution
after 3 hours?
Q.17. Silver crystallizes in a fcc lattice. The edge length of its unit cell is π. πππ Γ ππβπ
cm and its density is 10.5 g ππβπ. Calculate on this basis the atomic mass of silver.
(π΅π¨ π. ππ Γ ππππ πππβπ)
Q.18. What are food preservatives? Name two such substances.
Q.19. Give reasons:
(a) n-Butylbromide has higher boiling point than t-butyl bromide.
(b) Racemic mixture is optically inactive.
(c) The presence of nitro group (βπ΅πΆπ) at o/p positions increases increases the
reactivity of haloarenes towards nucleophilic substitution reactions.
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Q. 20. What are lyophilic and lyophobic sols? Give one example of each type. Which one of
these two types of sols is easily coagulated and why?
Q.21. What are biodegradable and non-biodegradable detergents? Give one example of
each class.
Q.22. The rate of a reaction becomes four times when the temperature changes from 293
K to 313 K. Calculate the energy of activation (π¬π)of the reaction assuming that it
does not changes with temperature. [πΉ = π. ππππ±π²βππππβπ, ππππ = π. ππππ].
Q.23. (a) Write the products formed when πͺπ―ππͺπ―πΆ reacts with the following
reactions:
(i) HCN
(ii) π―ππ΅ β πΆπ―
(iii) πͺπ―ππͺπ―πΆ the presence of dilute NaOH
(b) Give simple chemical tests to distinguish between the following pairs of
compounds:
(i) Benzoic acid and Phenol
(ii) Propanal and Propanone
OR
(a) Account for the following:
(i) πͺπ β πͺπ―ππͺπΆπΆπ― is a stronger acid than πͺπ―ππͺπΆπΆπ―.
(ii) Carboxylic acids do not give reactions of carbonyl group.
(b) Write the chemical equations to illustrate the following name reactions:
(i) Resenmund reduction
(ii) Cannizzaro's reaction
(c) Out of πͺπ―ππͺπ―π β πͺπΆβ πͺπ―π β πͺπ―π πππ πͺπ―ππͺπ―π β πͺπ―π β πͺπΆ β πͺπ―π which
gives iodoform test?
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Q.24. (a) Although pentoxide ion has more number of resonating structures than
Carboxylate ion, Carboxylic acid is a stronger acid than phenol. Give two
reasons.
(b) How will you bring about the following conversions?
(i) Propanone to propane
(ii) Benzoyl Chloride to benzaldehyde
(iii) Ethanal to but-2-enal
OR
(a) Complete the following reactions:
π ||
(i) 2π» β πΆ β π» Conc.KOH β
(ii) πΆπ»3πΆπππ» π΅π2/πβ
(iv)
(b) Give simple chemical tests to distinguish between the following pairs of
compounds:
(i) Ethanal and Propanol
(ii) Benzoic acid and Phenol
Q.25. (a) Illustrate the following name reactions giving a chemical equation in each case:
(i) Clemmensen reaction
(ii) Cannizzaroβs reaction
(b) Describe how the following conversions can be brought about:
(i) Cyclohexene to cyclohexene 1-one
(ii) Ethyl Benzene to benzoic acid
(iii) Bombazine to benzoic acid .
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OR
(a) Illustrate the following name reactions:
(i) Hell - Volhard - Zelinsky reaction
(ii) Wolff - Kishner reduction reaction
(b) How are the following conversions carried out:
(i) Ethyl Cyanide to ethanoic acid
(ii) Butan-1-o1 to butanoic acid
(iii) Methylbenzene to benzoic acid
Write chemical equations for the involved reactions.
Q. 26. (a) Illustrate the following name reactions:
(i) Cannizzaroβs reaction
(ii) Clemmensen reduction
(b) How would you obtain the following?
(i) But-2-enal from ethanal
(ii) Butanoic acid from butanol
(iii) Benzoic acid from ethylbenzene
OR
(a) Give chemical tests to distinguish between the following:
(i) Benzoic acid and ethyl benzoate
(ii) Benzaldehyde and acetophenone.
(b) Complete each synthesis by giving missing reagents or products in the following:
(i)
(ii) πͺππ―ππͺπ―πΆπ―ππ΅πͺπΆπ΅π―π΅π―πβ
(iii)
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