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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 ‘shape selective catalysis’

Q.2. Five the IUPAC name of the following compound.

𝐶𝐻2 = 𝐶 − 𝐶𝐻2𝐵𝑟 | 𝐶𝐻3

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:

(𝐂𝐇𝟑𝐂𝐇𝟐)𝟐𝐍𝐂𝐇𝟑

Q.6. State Raoult’s law for solutions, of volatile liquid components taking a suitable

example, explain the meaning of positive deviation from Raoult’s law.

OR

Define the term ‘osmotic pressure’. 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 𝟐. 𝟖 𝒈 𝒄𝒎−𝟑 forms a 𝒇. 𝒄. 𝒄. unit cell with edge length

𝟒 × 𝟏𝟎−𝟖𝒄𝒎. Calculate the molar mass of the element.

(Given: 𝑵𝑨 = 𝟔. 𝟎𝟐𝟐 × 𝟏𝟎𝟐𝟑𝒎𝒐𝒍−𝟏)

Q. 9. Draw the structures of the following molecules:

(i) 𝑿𝒆𝑶𝑭𝟒 (ii) 𝑯𝟑𝑷𝑶𝟑 .

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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?

𝑺𝑪𝟑+, 𝑽𝟑+, 𝑻𝒊𝟒+,𝑴𝒏𝟐+(𝐀𝐭. 𝐧𝐨𝐬. 𝐒𝐜 = 𝟐𝟏, 𝐕 = 𝟐𝟑, 𝐓𝐢 = 𝟐𝟐, 𝐌𝐧 = 𝟐𝟓)

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 𝟎. 𝟎𝟎𝟓𝟏 𝒎𝒊𝒏−𝟏. 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 𝟒. 𝟎𝟕𝟕 × 𝟏𝟎−𝟖

cm and its density is 10.5 g 𝒄𝒎−𝟑. Calculate on this basis the atomic mass of silver.

(𝑵𝑨 𝟔. 𝟎𝟐 × 𝟏𝟎𝟐𝟑 𝒎𝒐𝒍−𝟏)

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 (−𝑵𝑶𝟐) at o/p positions increases increases the

reactivity of haloarenes towards nucleophilic substitution reactions.




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 (𝑬𝒂)of the reaction assuming that it

does not changes with temperature. [𝑹 = 𝟖. 𝟑𝟏𝟒𝑱𝑲−𝟏𝒎𝒐𝒍−𝟏, 𝒍𝒐𝒈𝟒 = 𝟎. 𝟔𝟎𝟐𝟏].

Q.23. (a) Write the products formed when 𝑪𝑯𝟑𝑪𝑯𝑶 reacts with the following

reactions:

(i) HCN

(ii) 𝑯𝟐𝑵 − 𝑶𝑯

(iii) 𝑪𝑯𝟑𝑪𝑯𝑶 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) 𝑪𝒍 − 𝑪𝑯𝟐𝑪𝑶𝑶𝑯 is a stronger acid than 𝑪𝑯𝟑𝑪𝑶𝑶𝑯.

(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 𝑪𝑯𝟑𝑪𝑯𝟐 − 𝑪𝑶− 𝑪𝑯𝟐 − 𝑪𝑯𝟑 𝒂𝒏𝒅 𝑪𝑯𝟑𝑪𝑯𝟐 − 𝑪𝑯𝟐 − 𝑪𝑶 − 𝑪𝑯𝟑 which

gives iodoform test?




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:

𝑂 ||

(i) 2𝐻 − 𝐶 − 𝐻 Conc.KOH →

(ii) 𝐶𝐻3𝐶𝑂𝑂𝐻 𝐵𝑟2/𝑃→

(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) Cannizzaro’s 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 .




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) Cannizzaro’s 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) 𝑪𝟔𝑯𝟓𝑪𝑯𝑶𝑯𝟐𝑵𝑪𝑶𝑵𝑯𝑵𝑯𝟐→

(iii)




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cbse 12th chemistry unsolved overall important question

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