(NEW) CBSE Class 12 Chemistry Sample Paper
Half Yearly Examination (2019-20)
Time: 3:00 hour/ M.M.-70
- 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?
12- What is the unit of mole fraction?
d) none of these
13- Which element is a strong oxidizing agent in +3 oxidation state?
14- Choose the correct increasing order of acidic character?
d) none of these
15- What is the value of van’t hoff factor if there is neither dissociation nor association?
16- Which hydrides represent highest basic strength?
17- Which type of structure represent by XeOF4?
a) Square pyramidal
b) Square planar
18- Which hydrides have the largest bond angle?
19- Time-1is the unit of which type of order of reaction-
d) none of these
20- Which is not a cause of gas-liquid solutions-
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
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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