CBSE 12th Chemistry Unsolved Overall important Question Paper - … · 2019. 12. 31. · Tips, Tricks, General Knowledge, Current Affairs, Latest Sample, Previous Year, Practice Papers

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CBSE 12th Chemistry

Unsolved Overall important Question Paper - IV

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CBSE 12th Chemistry

Unsolved Overall Important Question Paper -IV

Q.1. If NaCl is doped with 𝟏𝟎−𝟑 mol % of 𝑺𝒓𝑪𝒍𝟐, What is the concentration of cation

vacancies?

Q.2. 1.00 g of a – non electrolyte solute dissolved in 50 benzene lowered the freezing point

of benzene by 0.40 K. The freezing point depression constant of benzene is 5.12 K

Kg 𝑴𝒐𝒍−𝟏. Find the mass of the solute.

Q.3. Give reason why a finely divided substance is more effective as an adsorbent.

Q.4. Name the common elements present in the anode mud in electrolytic refining of

copper. Why are they so present?

Q.5. Give the IUPAC name of following compound:

𝑪𝑯𝑭𝟐𝑪𝑩𝒓𝑪𝒍𝑭

Q.6. 45 g of ethylene glycol {𝑪𝟐𝑯𝟔𝑶𝟐} is mixed with 600 g of water. Calculate (a) the

freezing point depression and (b) the freezing point of the solution.

Q.7. Show that in a first order reaction, time required for completion of 99.9% is 10

times of half-life (𝒕𝟏/𝟐) of the reaction.

Q.8. Copper can be extracted by hydrometallurgy but not zinc. Explain.

Q.9. How will you bring about the following conversions?

(i) Propene to propyne

(ii) Toluene to benzyl alcohol

Q.10. Which compound in each of the following pairs will react faster in 𝑺𝒏𝟐 reaction with

- OH?

(i) 𝑪𝑯𝟑𝑩𝒓 𝒐𝒓 𝑪𝑯𝟑𝑰 (ii) (𝑪𝑯𝟑)𝟑𝑪𝑪𝒍 𝒐𝒓 𝑪𝑯𝟑𝑪𝒍

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Q.11. Explain what is observed?

(i) When a beam of light is passed through a colloidal sol.

(ii) An electrolyte, NaCl is added to hydrated ferric oxide sol.

(iii) Electric current is passed through a colloidal sol?

Q.12. Calculate the vapor pressure of the solution prepared by mixing 25.5 g of 𝑪𝑯𝑪𝒍𝟑

and 40 g of 𝑪𝑯𝟐𝑪𝒍𝟐 at 298 K?

Q.13. Write chemical reactions taking place in the extraction of zinc from zinc blende.

Q.14. Describe the manufacture of H2SO4 by contact process?

Q.15. mol−1 respectively, how can your account for the formation of a large number of

oxides having O2− species and not O−? (Hint: Consider lattice energy factor in the

formation of compounds).

Q.16. Write down the electronic configuration of:

(i) 𝑪𝒓𝟑+

(ii) 𝑷𝒎𝟑+

(iii) 𝑪𝒖+

(iv) 𝑪𝒆𝟒+

(v) 𝑪𝒐𝟐+

(vi) 𝑳𝒖𝟐+

Q.17. Write structure of the compounds whose IUPAC names are as follows:

(i) 1- Ethoxypropane

(ii) 2-Ethoxy-3-Methylpentane

(iii) Cyclohexylmethanol

(iv) 3-cyclohexylpentan-3-ol

(v) Cyclopent-3-en-1-ol

Q.18. Write short notes on the following:

(i) Carbylamine reaction

(ii) Hofmann’s bromamide reaction

Q.19. What are monosaccharides?

OR

What are enzymes?




Q.20. Write the names and structures of the monomers of the following polymers:

(i) Buna-S

(ii) Buna-N

(iii) Dacron

Q.21. Copper crystallises into a fcc lattice with edge length 𝟑. 𝟔𝟏 × 𝟏𝟎−𝟖 cm. Show that

the calculated density is in agreement with its measured value of 8.92 g 𝑪𝒎𝟑.

Q.22. From the rate expression for the following reactions. Determine their order of

reaction and the dimensions of the rate constants.

(i) 𝟑𝑵𝑶(𝒈) → 𝑵𝟐𝑶 (𝒈) 𝑹𝒂𝒕𝒆 = 𝒌[𝑵𝑶]𝟐

(ii) 𝑯𝟐𝑶𝟐 {𝒂𝒒} + 𝟑𝑰− (𝒂𝒒) + 𝟐𝑯+ → 𝟐𝑯𝟐𝑶 (𝟏) + 𝑰𝟑−𝑹𝒂𝒕𝒆 = 𝒌[𝑯𝟐𝑶𝟐][𝑰−]

(iii) 𝑪𝑯𝟑𝑪𝑯𝑶 (𝒈) → 𝑪𝑯𝟒 (𝒈) + 𝑪𝑶(𝒈)𝑹𝒂𝒕𝒆 = 𝒌[𝑪𝑯𝟑𝑪𝑯𝑶] 𝟑/𝟐

Q.23. Using IUPAC norms write the systematic names of the following:

(i) [𝑪𝒐(𝐻2𝒐)(𝑪𝑵)(𝑬𝒏)𝟐]𝟐+

(ii) [𝑷𝒕(𝑵𝑯𝟑)𝟐𝑪𝒍(𝑵𝑯𝟐𝑪𝑯𝟑)]𝑪𝒍

(iii) [𝑻𝒊(𝑯𝟐𝟎)𝟔]𝟑+

(iv) [𝑪𝒐(𝑵𝑯𝟑)𝟒𝑪𝒍(𝑵𝒐𝟐)]𝑪𝒍

(v) [𝑴𝒏(𝐻2𝒐)𝟔]𝟐+

(vi) [𝑵𝒊(𝐶𝑙4]𝟐−

OR

Name the oxometal anions of the first series of the transition metals in which the metal

exhibits the oxidation state equal to its group number?

Q.24. Consider a certain reaction A → Products with k = 2.0 × 10−2 s−1.

Calculate the concentration of a remaining after 100 s if the initial concentration of

A is 1.0 mol L−1.

OR

A reaction is first order in A and second order in B.

(i) Write the differential rate equation.

(ii) How is the rate affected on increasing the concentration of B three times?

(iii) How is the rate affected when the concentrations of both A and B are doubled?




Q.25. (i) Nitrogen exists as diatomic molecule and phosphorus as P4. Why?

(ii) How are 𝑿𝒆𝑶𝟑 and 𝑿𝒆𝑶𝑭𝟒 Prepared?

(iii) Arrange the following in the order of property indicated for each set:

a) F2, Cl2, Br2, I2 - increasing bond dissociation enthalpy.

b) HF, HCl, HBr, HI - increasing acid strength.

c) NH3, PH3, AsH3, SbH3, BiH3 − increasing base strength.

OR

(i) Justify the placement of O, S, Se, Te and Po in the same group of the periodic

table in terms of electronic configuration, oxidation state and hydride

formation.

(ii) Write balanced equations for the following:

a. NaCl is heated with sulphuric acid in the presence of MnO2.

b. Chlorine gas is passed into a solution of NaI in water

Q.26. (i) Explain the following with an example.

a) Kolbe’s reaction.

b) Reimer-Tiemann reaction.

(ii) Describe the following:

a) Cannizzaro reaction:

b) Decarboxylation:

OR

(i) Complete each synthesis by giving missing starting material, reagent or

products?

(ii) Write equations of the following reactions:

a) Friedel-Crafts reaction−alkylation of anisole.

b) Nitration of anisole.

c) Bromination of anisole in ethanoic acid medium.




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CBSE 12th Chemistry Unsolved Overall important Question Paper - … · 2019. 12. 31. · Tips, Tricks, General Knowledge, Current Affairs, Latest Sample, Previous Year, Practice Papers