CBSE Sample Papers for Class 12 Chemistry Solved 2016 Set 14

Section A

2.Arrange the following compounds in the increasing order of their reactivity in nucleophilic addition reactions.

Ethanal, propanal, propanone, butanone.

3.p-dichlorobenzene has higher melting point and lower solubility than those of o and m-isomers. Discuss.

4. Explain non-stoichiometric defects with suitable examples.

5. Give the structures and IUPAC names of monohydric phenols of molecular formula C₇H_sO.

Section B

Section C

11.(i) Why is the use of aspartame limited to cold foods and drinks? (l)

(ii) (a) What are steroids? Give an example.

(b) Give some important uses of chloramphenicol.

12.(i) How can you obtain iodoethane from ethanol, when no other iodine containing

reagent except Nal is available in the laboratory?

(ii) Write a test to detect the presence of double bond in a molecule.

(iii) Write short note on Swarts reaction.

13.(i) Write the mechanism of acid dehydration of ethanol to yield ethene.

(ii) Explain, Etard reaction with an example.

(iii) Why is o -nitrophenol more acidic than o -methoxyphenol?

14.Determine the amount of CaCl₂ (i = 2.47) dissolved in 2.5 L of water such that its osmotic pressure is 0.75 atm at 27°C [R = 0.0821 L atm mol^-1 K^-1]. (3)

Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K₂S0₄ in 2L of water at 25°C, assuming that it is completely dissociated [R = 0.0821L atm mol^-1 K^-1].

15.How much electricity is required in Coulomb for the oxidation of

1 mole of H₂0 to 0₂ ?
1 mole of FeO to Fe₂0₃?
1 mole of MnO^–toMn²⁺?

16. Give reasons for the following :

Zinc oxide can be reduced to the metal by heating with carbon but not Cr₂0₃. (l)
Alumina is dissolved in cryolite for electrolysis instead of being electrolysed directly.

Extraction of copper directly from sulphide ores is less favourable than that from its oxide ore through reduction.

17. State reasons for the following :

Of the d⁴ species, Cr²⁺ is strongly reducing while, manganese (III) is strongly oxidising.

The d¹ configuration is very unstable in ions. (l)
Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents, it is easily oxidised.

18. Dimethyl glyoxime is added to alcoholic solution of NiCl₂. When ammonium hydroxide is slowly added to it, a rosy red precipitate of a complex appears.

Give the structure of the complex showing hydrogen bonds.
Give oxidation state and hybridisation of central metal ion.
Identify, whether it is paramagnetic or diamagnetic.

19.(i) Why is adsorption exothermic?

(ii) What is the effect of temperature on chemisorption? Explain.

(iii) What is the significance of reciprocal of “gold number”.

20.(i) Explain the difference between buna-N and buna-S.

(ii) Arrange the following polymers in increasing order of their intermolecular forces.

Nylon-6, 6, buna-S, polythene.
Nylon-6, neoprene, polyvinyl chloride (PVC).

21.(i) Bond angle in PH4 is higher than in PH₃ . Why?

Electron gain enthalpy is less for fluorine than for chlorine. Why? (l)
Both 0₂ and F₂ stabilise high oxidation states but the ability of oxygen to stabilise the higher oxidation state exceeds than that of fluorine. Why?

22.(i) Explain, why does conductivity of germanium crystals increases on doping with galium?

(ii) What do you mean by metal excess defect? Explain with an example.

Section D

23.Now a days, a new toothpaste ‘Parodontax’ is launched in the market for the cure of bleeding gum. Deficiency of vitamin C is responsible for a disease called scurvy, a disease of gums.

Read the given passage and give answer to the following questions.