(NEW) CBSE Class 12 Chemistry Sample Paper

Half Yearly Examination (2019-20)


Time: 3:00 hour/ M.M.-70

Sub- Chemistry

General Instructions:

  • All questions are compulsory.
  • Questions 1 to 20 are very short answer questions and carry 1 mark each.
  • Questions 21 to 27 are short answer questions and carry 2 marks each.
  • Questions 28 to 34 are also short answer questions and carry 3 marks each.
  • Questions 35 to 37 are long answer questions and carry 5 marks each.
  • Use log tables if necessary, use of calculators are not allowed.

1- Draw the structure of 2, 6-dimethylphenol.

2- What is denatured alcohol?

3- What is known as a racemic mixture? Give an example.

4- Zn+2 salts are colourless. Why?

5- What is nitrous acid an oxidant as well as a reductant?

6- How is SO2 an air pollutant?

7- Why conductivity of an electroyle solution decreases with the decreases in concentration?

8- Write nerest equation for the general cell reaction


9- Define Ideal solution and write one of its main characteristics.

10- What is similarity between Roault’s law and Henery’s law?

11- Which element has the highest melting point?

a) Mn

b) Fe

c) Cr

d) Zn

12- What is the unit of mole fraction?

a) molL-1

b) molKg-1

c) mole

d) none of these

13- Which element is a strong oxidizing agent in +3 oxidation state?

a) Mn

b) Fe

c) Cr

d) Zn

14- Choose the correct increasing order of acidic character?

a) Cr2O3<CrO3<CrO

b) CrO3<Cr2O3<CrO

c) CrO<Cr2O3<CrO3

d) none of these

15- What is the value of van’t hoff factor if there is neither dissociation nor association?

a) i<1

b) i>1

c) i=1

d) i=0

16- Which hydrides represent highest basic strength?

a) AsH3

b) PH3

c) BiH3

d) NH3

17- Which type of structure represent by XeOF4?

a) Square pyramidal

b) Square planar

c) pyramidal

d) Linear

18- Which hydrides have the largest bond angle?

a) H2O

b) H2S

c) H2Se

d) H2Te

19- Time-1is the unit of which type of order of reaction-

a) I

b) II

c) Zero

d) none of these

20- Which is not a cause of gas-liquid solutions-

a) Pressure

b) Temperature

c) Solvation

d) Nature of gas

21- Write the mechanism of the following reaction-

CH3CH2OH     ———————–CH3CH2Br +H2O

22- Give the structural formula and IUPAC name of the following compounds-

a) BHC b) DDT

23- Gives one use of each -Freon-12, CCl4, BHC, Iodoform.

24- Write the hybridsation types ND Magnetic behavior of the complex: [Ni(CN)4]2– and [Fe(CO)5].

25- [NiCl4]2– is paramagnetic while [Ni(CO)4] is diamagnetic though both are tetrahedral why?

26- Giving examples differentiate between roasting and calcinations.

27- What is shape selective catalysis? Explain.

28- Henry’s law constant for CO2 in water is 1.67×108 Pa at 298K.Calculate the quantity of CO2 in 500ml of soda water when packed under 2.5 atm CO2 pressure at 298K.

29- (a) The conductivity of 0.20molL-1 solution of KCl is 2.48×10-2 SCm-1.Calculate its molar conductivity and degree of dissociation (α). Given λ0 (K+) =73.5 Scm2 mol-1 and λ0 (Cl)=76.5 Scm2 mol-1

(b) What type of battery is mercury cell. Why is it more advantageous than dry cell?

30- Define the term-

a) Froth floatation process

b) Coagulation

c) Hardy-Schulze rule

31- An organic compound ‘A’ having molecular formula C3H6 on treatment with aqueous H2SO4 gives ‘B’ which on treatment with HCl/ZnCl2 gives ‘C’. The compound ‘C’ on treatment with ethanolic KOH gives back the compound ‘A’. Identify the compound A,B,C.

32- Give reason for the following-

a) C-X bond length in halobenzene is smaller than C-X bond length in CH3-X.

b) Haloalkanes easily dissolve in organic solvents.

33- Giving a suitable example for each explain the following-

a) Crystal field splitting

b) Linkage isomerism

c) Ambidentate ligand

34- (a) Draw the structures of (i)BrF5 (ii)XeF4

34- (b) Why are halogens considered strong oxidising agents?

35- (a) A reaction is second order in A and first order in B.

i) Write the differential rate equation.

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

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

35- (b) A first order reaction takes 40 minutes for 30%decomposition. Calculate t½ for this reaction(Given log1.428=0.1548)

36- (a) Write the law and application of Kohlrausch’s law.

36-(b) A 5%solution of cane sugar in water has a freezing point of 271 K Calculate the freezing point of a 5% glucose in water if the freezing point of pure water is 273.15 K.

37- How would you obtain the following-

a) Ethanol to propanenitrile

b) Propan-2-ol from propene

c) Phenol to aspirin

d) Benzene to diphenyl

e) Aniline to Phenol

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