Board Paper of Class 12-Science 2011 Chemistry (SET 3) - Solutions
General Instructions:
(i) All questions are compulsory
(ii) Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv) Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v) Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi) Use Log Tables, if necessary. Use of calculators is not allowed.
- Question 3
What type of ores can
be concentrated by magnetic separation method?
VIEW SOLUTION
- Question 4
Write the IUPAC name of
the following compound: CH2 = CHCH2Br
VIEW SOLUTION
- Question 8
Give a chemical test to
distinguish between ethylamine and aniline.
VIEW SOLUTION
- Question 9
Calculate the packing
efficiency of a metal crystal for a simple cubic lattice.
VIEW SOLUTION
- Question 10
Explain how you can
determine the atomic mass of an unknown metal if you know its mass
density and the dimensions of unit cell of its crystal.
VIEW SOLUTION
- Question 11
Differentiate between molarity and molality values for a solution. What is the effect of change in temperature on molarity and molality values?
VIEW SOLUTION
- Question 12
The thermal
decomposition of HCO2H is a first order reaction with a
rate constant of 2.4 × 10−3 s−1
at a certain temperature. Calculate how long will it take for
three-fourths of initial quantity of HCO2H to decompose.
(log 0.25 = −
0.6021)
VIEW SOLUTION
- Question 13
What do you understand
by the rate law and rate constant of a reaction?
Identify the order of a
reaction if the units of its rate constant are:
(i) L−1
mol s−1
(ii) L mol−1
s−1
VIEW SOLUTION
- Question 14
Describe the principle
controlling each of the following processes:
(i) Preparation
of cast iron form pig iron.
(ii) Preparation
of pure alumina (Al2O3) from bauxite ore.
VIEW SOLUTION
- Question 15
Explain giving reasons:
(i) Transition
metals and their compounds generally exhibit a paramagnetic
behaviour.
(ii) The
chemistry of actinoids is not so smooth as that of lanthanoids.
VIEW SOLUTION
- Question 16
Complete the following
chemical equations:
(i)
(ii)
OR
State reasons for the
following:
(i) Cu (I) ion
is not stable in an aqueous solution.
(ii) Unlike
Cr3+, Mn2+, Fe3+ and the subsequent
other M2+ ions of the 3d series of elements, the 4d and
the 5d series metals generally do not form stable cationic species.
VIEW SOLUTION
- Question 17
Write the main structural difference between DNA and RNA. Of the four bases, name those which are common to both DNA and RNA.
VIEW SOLUTION
- Question 18
Write such reactions
and facts about glucose which cannot be explained by its open chain
structure.
VIEW SOLUTION
- Question 19
A solution prepared by
dissolving 8.95 mg of a gene fragment in 35.0 mL of water has an
osmotic pressure of 0.335 torr at 25°C.
Assuming that the gene
fragment is a non-electrolyte, calculate its molar mass.
VIEW SOLUTION
- Question 20
Classify colloids where the dispersion medium is water. State their characteristics and write an example of each of these classes.
OR
Explain what is observed when
(i) an electric current is passed through a sol
(ii) a beam of light is passed through a sol
(iii) an electrolyte (say NaCl) is added to ferric hydroxide sol
VIEW SOLUTION
- Question 21
How would you account for the following:
(i) NF3 is an exothermic compound but NCl3
is not.
(ii) The acidic strength of compounds increases in the order:
PH3 < H2S < HCl
(iii) SF6 is kinetically inert.
VIEW SOLUTION
- Question 22
Write the state of
hybridization, the shape and the magnetic behaviour of the following
complex entities:
(i) [Cr(NH3)4
Cl2] Cl
(ii) [Co(en)3]
Cl3
(iii) K2
[Ni(CN)4]
VIEW SOLUTION
- Question 23
State reasons for the
following:
(i) pKb
value for aniline is more than that for methylamine.
(ii) Ethylamine
is soluble in water whereas aniline is not soluble in water.
(iii) Primary
amines have higher boiling points than tertiary amines.
VIEW SOLUTION
- Question 24
Rearrange the compounds
of each of the following sets in order of reactivity towards SN2
displacement:
(i) 2-Bromo-2-methylbutane,
1-Bromopentane, 2-Bromopentane
(ii) 1-Bromo-3-methylbutane,
2-Bromo-2-methylbutane, 3-Bromo-2-methylbutane
(iii) 1-Bromobutane,
1-Bromo-2, 2-dimethylpropane, 1-Bromo-2-methylbutane
VIEW SOLUTION
- Question 25
How would you obtain
the following:
(i) Benzoquinone
from phenol
(ii) 2-methyl
propan-2-ol from methyl-magnesium bromide
(iii) Propane-2-ol
from propene
VIEW SOLUTION
- Question 26
Write the names and
structures of the monomers of the following polymers:
(i) Buna-S
(ii) Dacron
(iii) Neoprene
VIEW SOLUTION
- Question 27
What are the following
substances? Give one example of each.
(i) Food
preservatives
(ii) Synthetic
detergents
(iii) Antacids
VIEW SOLUTION
- Question 28
(a) Draw the
structures of the following molecules:
(i) (HPO3)3
(ii) BrF3
(b) Complete the
following chemical equations:
(i) HgCl2
+ PH3 →
(ii) SO3
+ H2SO4 →
(iii) XeF4
+ H2O →
OR
(a) What happens
when
(i) chlorine
gas is passed through a hot concentrated solution of NaOH?
(ii) sulphur
dioxide gas is passed through an aqueous solution of a Fe (III) salt?
(b) Answer the
following:
(i) What is the
basicity of H3PO3 and why?
(ii) Why does fluorine not play the role of a central atom in
inter-halogen compounds?
(iii) Why do
noble gases have very low boiling points?
VIEW SOLUTION
- Question 29
(a) What type of a battery is lead storage battery? Write the anode and cathode reactions and the overall cell reaction occurring in the operation of a lead storage battery.
(b) Calculate the potential for half-cell containing 0.10 M K2Cr2O7 (aq), 0.20 M Cr3+ (aq) and 1.0 × 10−4 M H+ (aq)
The half-cell reaction is and the standard electrode potential is given as E0 = 1.33 V.
OR
(a) How many moles of mercury will be produced by electrolysing 1.0 M
Hg (NO3)2 solution with a current of 2.00 A for 3 hours?
[Hg(NO3)2 = 200.6 g mol−1]
(b) A voltaic cell is set up at 25°C with the following half-cells Al3+ (0.001 M) and Ni2+ (0.50 M). Write an equation for the reaction that occurs when the cell generates an electric current and determine the cell potential.
VIEW SOLUTION
- Question 30
(a) Illustrate
the following name reactions:
(i) Cannizzaro’s
reaction
(ii) Clemmensen
reduction
(b) How would
you obtain the following:
(i) But-2-enal
from ethanal
(ii) Butanoic
acid from butanol
(iii) Benzoic
acid from ethylbenzene
OR
(a) Given
chemical tests to distinguish between the following:
(i) Benzoic
acid and ethyl benzoate
(ii) Benzaldehyde
and acetophenone
(b) Complete
each synthesis by giving missing reagents or products in the
following:
(i)
(ii)
(iii)
VIEW SOLUTION