AHSEC| CLASS 12| CHEMISTRY| QUESTION PAPER - 2015| H.S. 2ND YEAR
2015
CHEMISTRY
(Theory)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate full marks for the questions.
1. Answer the following: 1x8=8
(i) Which point
defect lowers the density of a crystal?
(ii) Liquid-liquid
sols are known as _______. (Fill in the blank)
(iii) Which
metal foils are used for wrapping chocolates?
(iv) In the
first transition series of elements, which element shows highest oxidation
state?
(v) Write the
formula for the co-ordination compound: tetracarbonylnickel (o).
(vi) Mention one
use of tetrachloromethane.
(vii) Give
the IUPAC name of the following compound:
CH2=CH-CH2-CHO
(viii) Name one
water soluble vitamin.
2. State Henry’s law.
At the same
temperature, hydrogen gas is more soluble in water than helium gas.
Which one of
them will have higher value of KH? 2
3. Define molar conductivity of an electrolytic solution.
How does molar conductivity vary with concentration for weak electrolyte? 2
Or
The limiting
molar conductance’s of sodium chloride, hydrochloric acid and sodium acetate
are 126.45, 426.16 and 91.0. Scm2mol-1 respectively at
298 K. Calculate the limiting molar conductance of acetic acid at 298K.
4. Distinguish between calcination and roasting. 2
5. What are transition elements? Give the general electronic
configuration of transition elements. 2
6. What are alloys? Name the metals used for the formation
of bronze. 2
Or
Explain the
following: 1+1=2
(i) Transition
metals and their compounds can act as catalyst.
(ii) In the
titration of FeSO4 with KMnO4 in acidic medium, dilute
HCL is not used.
7. Give one example each of the following: 1+1=2
(i) Ionisation
isomerism
(ii) Geometrical
isomerism
Or
Using valence
bond theory, show that [Ni(CN)4]2- complex ion is
diamagnetic in nature. [Atomic number of Ni is 28].
8. Explain why: (Any Two) 1+1=2
(i) Phenols are
acidic in nature.
(ii) Ethers have
lower boiling points than alcohols.
(iii) Propan-2-ol
is more basic than propan-1-ol.
9. Complete the following reactions: 1+1=2
10. Answer the following: 1+1=2
(a) Arrange in
increasing order of basic strength:
CH3NH2
(CH3)2 NH (CH3)3N (in aqueous
solution)
(b) Kb
value of aniline is less than that of methyl amine. Why?
11. Give the formulae of A, B, C and D in the following
reactions – 1+1=2
12. (a) For one mole close packed spheres, how many
octahedral and tetrahedral voids are present? 1
(b) Atoms of
element X form hcp lattice and those of element Y form occupy 2/3rd
of the tetrahedral voids. Determine the formula of the compound formed by the elements
X and Y? 2
13. (a) What is an ideal solution? 1
(b) Urea [(NH2)2CO]
forms an ideal solution in water. Calculate the vapour pressure of an aqueous
solution containing 5% by mass of urea at 298K. At 298K, vapour pressure of
water is 23.75mm Hg. 2
Or
The vapour
pressure of pure liquids A and B are 450mm Hg and 700mm Hg respectively at
350K. If the total vapour pressure of the mixture of the two liquids at 350K is
600mm Hg, calculate the mole fractions of the two components in the solution.
Also, calculate the partial pressures of the two components in the vapour
phase. 2+1=3
14. What is corrosion? Give two measures for the prevention
of corrosions of metals. 1+2=3
15. What are adsorption and absorption processes? Give one
suitable example to show the distinction between the two. 2+1=3
Or
Define
homogeneous and heterogeneous catalysis. Give one suitable example each of the
two catalysis. 2+1/2x2=3
16. (a) Mention one use each of Argon and Helium
gases. 2
(b) Name the
noble gas that forms majority of the known noble gas compounds. 1
17. Complete the following equations: 1x3=3
(a) C2H5OH
+ SOCI2 –>
?
18. What are carbohydrates? Give the general formula of
carbohydrates. Why are polysaccharides called non-sugars? 1+1+1=3
Or
What are proteins?
Give one example each of fibrous and globular proteins.
19. (a) What are polymers? 1
(b) Name the
monomers of polythene, Teflon, and Nylon-6, 6. 1/2x4=2
Or
(a) What is
vulcanisation of rubber? 2
(b) What is the
role of sulphur on vulcanisation of rubber? 1
20. Give one example each of the following: 1x3=3
(a) A
non-narcotic analgesic.
(b) An
artificial sweetner.
(c) A food
preservative chemical.
Or
(i) Mention one
advantage of the use of synthetic detergent over soap. 1
(ii) What is
tincture of iodine? Mention one use of tincture of iodine. 1+1=2
21. Answer either (a) or (b):
(a) (i)
Define order of a reaction. 1
(ii) For the
reaction R –> P, write the differential rate law. 1
(iii) For the
reaction R –> P, the rate becomes 4 times faster when the concentration of
the reactant R is doubled at a given temperature. When is the order of the
reaction? 2
(iv) Define
activation energy of a reaction. 1
Or
(b) (i)
Show that the integrated rate law for the first order reaction
(ii) A first
order reaction takes 40 minutes for 20% decomposition. Calculate its half
period. 2
22. Answer either (a) and (b), or (c) and (d).
(a) Give
reasons for the following: 1x3=3
(i) Nitrogen
exhibits +5 oxidation state But it does not form pentahalide.
(ii) Sulphur
vapour is paramagnetic.
(iii)
Moist chlorine is powerful bleaching agent.
(b)
Complete the following reasons – 1+1=2
(i)
P4 + 3NaOH + 3H2O –>?
(ii)
2F2(g) + 2H2O(l) –>?
(c) Describe the manufacture of ammonia by Haber’s process with favourable conditions. 3
(d)
Draw the structures of the following molecules: 2
(i)
XeF4
(ii) H3PO3
23. (a) How will you bring about the following
conversions? (give chemical equations only): 2
(i) Toluene to
benzaldehyde.
(ii)
Ethanenitrile to ethanoic acid.
(b) Identify
A, B, C and D in the following reactions: 2
(c) Name one
biodegradable polymer.
***
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