CBSE chemistry sample apers

Document Sample
CBSE chemistry sample apers Powered By Docstoc
					CBS E C hemi str y S am ple Que stion P aper
- Yea r 2000

Filed under:

  •    Class XII
  •    Chemistry

         Chemis tr y C las s - XII (CB SE )
      You ar e on Se t 1 ques tions 1 to 20

Q.1 What is the physical significance of the
lines in the following depiction of atomic
orbitals? (Ma r k 1)

Q.2 An ionic compound AB2 possesses CaF2
type crystal structure. Write the co-
ordination numbers of A2+ and B- ions in the
crystals of AB2. (AB2+ = 8, B- = 4 ) (Ma r k 1)

Q.3 How many state of a thermodynamic
system be defined? (Ma r k 1)

Q.4 State Kohlrausch’s law for electric
conductance of an electrolyte at infinite
dilution. (Mar k 1)

Q.5 For the reaction 3N2 (g) + H2 (g) —-> 2NH3
(g), how are the rate of reaction expression
-d[H2]/ dt and d[NH3]/dt interrelated? (Ma r k

Q.6 Mention the use of fromalin in industry.
(Mar k 1)

Q.7 For an amine RNH2 write the expression
for Kb to indicate its base strength. ( Mar ks

Q.8 What is responsible for the blue colour of
a solution of an alkali metal in liquid
ammonia? (Mar k 1)

Q.9 Why do colloidal solution exhibit Tyndall
effect? (Ma r k 1)

Q.10 Write any one characteristics feature
of enzymatic catalysts. (Mar k 1)

Q.11 Account for the following :
(i) Silicon is an insulator but silicon doped
with phosphorous acts as a semiconductor.
(ii) Some of the glass objects recovered from
ancient monuments look milky instead of
being transparent. (Mar k 2 )

Q.12 Give an example each of miscible liquid
pairs showing positive and negative deviation
from Raoult’s law. Give one reason each for
deviation. ( Mar k 2)

Q.13 Starting with thermodynamic
relationship E = q - P V and H =E + PV derive
the relationship H = qp (Mar k 2 )

Q.14 From the data given below at 298 K for
the reaction :
CH4 (g) + 2O2 (g) ——> CO2 (g) + 2H2O (l)
Calculate the enthalpy of formation of CH4 (g)
at 298 K.
Enthalpy of reaction = - 890.5 kJ
Enthalpy of formation of CO2 (g) = - 393.5 kJ
Enthalpy of formation of H2O (l) = - 286.0 kJ
mol-1 (Ma r k 2)

Q.15 Give the IUPAC names of :
Ima ge no .1
(Mar k 2 )

Q.16 Give explanation for the following
observation :
(i) An ether would possess a dipole moment
even if the alkyl groups present in it are
(ii) Towards nucleophilic reagents aldehydes
are more reactive tan ketones. (Ma r k 2)

Q.17 For the following conversion reaction
write the chemical equations :
(i) Ethyl isocyanide to ethylamine
(ii) Aniline to N-phenylthanamide(Mar k 2 )

Q.18 Account for the following :
(i) Ammonolysis of alkylhalides does not give
a corresponding amine in pure state.
(ii) If -NO2 or -COOH groups is attached to a
carbon of benzene ring, electrophilic
substitution becomes difficult. ( Mar ks 2 )
Q.19 The sum of first and second ionisation
energies and those of third and fourth
ionisation energies of nickel and platinum are
given below :

     I E + IE2(MJ mol-      I E3 + IE4(MJ
               )                mol-1)

           2.49                  8.80

           2.66                  6.70
alues into account write :
(i) The most common oxidation state are for
Ni and Pt and its reason.
(ii) The name of metal (Ni and Pt) which can
form compound in +4 oxidation more easily
and why. ( Mar ks 1)

Q.2 0 (i) Of the ions Ag+, Co2+ and Ti+, which
ones will be coloured in aqueous solution
(Atomic numbers : Ag = 47, Co = 27, Ti = 22)
(ii) If each one of the above ionic species is
in turn place in a magnetic field,
How will ir respond and why? (Ma r ks 2)

Q.21 Among ionic species, Sc3+, Ce2+ and
Ti4+, which ones will be occurred in aqueous
solution? (Atomic number : Sc = 21, Ce = 58,
Eu = 63) (Mar ks 2 )

Q.2 2 Explain the following processes with a
suitable example in each case :
(i) Chain - growth polymerisation
(ii) Step - growth polymerisation (Mar ks 2 )

Q.2 3 Given an example of each, differentiate
between multi-molecular and
macromolecular colloides. ( Mar ks 2 )

Q.2 4 What are polysaccharides? Name one
of the. How is it important for us. (Ma r ks 2)

Q.25 What do you understand by the
statement : “ATP molecules are the currency
of energy metabolism in a cell.” (Ma r k 2)

Q.26 Name the broad spectrum antibiotic
and state two diseases for which it is
prescribed. (Ma r k 2)

Q.27 The ionisation energy of hydrogen atom
in ground state is 1312 kJ mol-1. Calculate
the wavelength of radiation emitted when the
electron in this atom makes a transition from
n = 2 state to n = 1.
(Planks constant, h = 6.63 x 10-34 Js, velocity
of light = 3 x 1010 cm s-1 and Avogadro
number, NA = 6.02 x 1023 mol-1) ( Mar ks 3 )

Q.2 8 On dissolving 3.24g of sulphur in 4.0g
of benzene boiling point of solution was
higher than that of benzene by 0.81 K. Kb
value for benzene is 2.53 K kg mol-1. What is
the molecular formula of sulphur ? (Atomic
mass of sulphur = 32 g mol-1) (Ma r ks 3)
Q.29 Calculate the cell emf and Ima ge n o.3
G for the cell reaction at 25oC for the cell
Zn (s) | Zn2 + (0.0004 M) || Cd2+ (0.2 M) | Cd (s)
Eo values at 25o C : Zn2+ / Zn = - 0.763 V ;
Cd2+/ Cd = -0.403 V;
F = 96500 C mol-1; R = 8.314 JK -1. ( Mar ks 3 )

Q.3 0 Describe how important functions each
of the elements P, B and S in green plants
and also write the deficiency symptoms of
any two of them. (Ma r ks 3)

Q.31 Describe the following :
(i) Optical isomerism.
(ii) Magnetic behaviour of [Ni(CN)4]2- ion. (At.
No. of Ni =28)
(iii) Preparation of tetrabutyl tin (Ma r ks 3)

Q.3 2 (i) What is nuclear fission reaction
(ii) Describe the basic principle of a nuclear
reactor? (Ma r ks 3, 2)

Q.3 3 (a) Write chemical equation and
reaction conditions for the conversion of :
(i) Propane to 1-bromo-propane
(ii) Chlorobenzene to phenol
(iii) 2-propanol to iodoform
(b) How is glycerol obtained commercially,
state its two uses. (Ma r k 3)

Q.3 4 (a) Account for the following
observation :
(i) In several chemical properties lithium
resembles magnesium.
(ii) +1 oxidation state of thallium (atomic no
81) is more stable than its +3 oxidation state.
(iii) Boron chloride exists as a monomer while
in the same group anhydrous aluminium
chloride exists as adimer.
(b) Complete and balance the following
chemical equation :
(i) NH3 + NaOCl —->
(ii) XeF4 + SbF5 (Ma r k 3, 2 )

CBS E C hemi str y S am ple Que stion P aper
- Yea r 1999

Filed under:

  •   Class XII
  •   Chemistry

      Chemis tr y C las s - XII (CB SE )
  You ar e on qu es tions 1 t o 2 0 of Se t I

Q.1 Define an atomic orbital. What does
angular momentum quantum number tell
about an orbital ? (1 m ar k)

Q.2 Which one of the two, O-2 or O 2-2 has
higher bond order and why?(1 m ar k)

Q.3 Define dislocation in crystal. (1 ma r k)

Q.4 Write an example of neutral molecule
which is isoelectronic to CIO-.
(1 ma r k)

Q.5 Express the relationship between degree
of dissociation of an electrolyte and its
molar. Conductivity. (1 m ar k)

Q.6 What for are quaternary ammonium salts
widely used? (1 ma r k)

Q.7 What is meant by Faraday constant? (1
mar k)

Q.8 Define the “Ligand". Give an example
also. (1 ma r k)

Q.9 Give an example of the compound in
which hydrogen bonding results in the
formation of adimer. (1 m ar k)

Q.10 Write an general formula by which the
electronic configurations of the transitions
element is represented. (1 ma r k)

Q.11 Calculate the uncertainty in the
position of an electron if the uncertainty in
its velocity is 5.7 x 105 ms-1. (h = 6.6 x 10-34 Js
and mass of electron = 9.1 x 10-31kg) (1
mar k)

Q.12 (i) What is the basic building unit of
(ii) Draw the structure of asbestos (a silicate
containing SiO2-3 anions).(2 m ar ks)
Q.13 State Rault’s law. Discuss the factors
responsible for the deviation from this low. (2
mar ks)

Q.14 Calculate the molarity and molality of a
15% solution (by weight) of sulphuric acid of
density 1.020 g cm-3. (Atomic masses : H = 1,
O = 16, S = 32 amu) (2 m ar ks)

Q.15 Derive the following equation : (2
mar ks)
D H = DE + ( Dn) RT

Q.16 A first order reaction is 15% complete
in 20 minutes. How long will it take to be 60%
complete. ( 2 ma r ks)

Q.17 Calculate the potential of a zinc-zinc
ion electrode in which the zinc ion activity is
0.001 M.
(EoZn2+/Zn. = – 0.76 V, R = 8.314 JK-1 mol-1, F =
96,500 mol-1) (2 m ar ks )

Q.18 Nitric oxide reacts with hydrogen to
give nitrogen and water.
2 NO + 2 H2 –> N2 + 2 H2O
The kinetics of this reaction is explained by
the following steps :
(i) 2 NO + 2 H2 –> N2 + 2 H2O (slow)
(ii) H2O2 + H2 –> 2 H2O (fast)
What is the predicted rate low ? (2 m ar ks )

Q.19 Write the IUPAC names of the following compounds.


Q.20 Write the reaction involved in the preparation of benzene daizonium

chloride. What happens when benzene daizonium chloride reacts with (i)

Cu2Cl2 and (ii) phenol ?(Given equation for the reaction) (2 m ar ks )

Q.21 Account for the following : (2 m ar ks )

(i) Alkylamines are stronger bases than arylamines.

(ii) Toluene is more easily nitrated than benzene.

Q.22 (i) Why do the transitional metals slow variability in their oxidation


(ii) Write formula of a compound where the transitional metal is in +7 oxidation

state. (2 m ar ks )

Q.23 Draw the structure and write the hybridisation state of the central atom

of each of the following species :

(i) Fe(CO)5
(ii) trans-[CO(NH3)4Cl2]       (Atomic Number : Fe = 26, CO = 27) (2 m ar ks )

Q.2 4 What happens during glycolysis and what are the products of

glycolysis ? (2 ma r ks)

Q.25 What are antibiotics? Name any two antibiotics which are specific for

certain diseases. (2 marks)

Q.26 How are Buna-S and Terylene synthesised? Give chemical equations.(2

mar ks )

Q.27 When 0.532 g of benzene (C6H6), boiling point of 353 K, is burnt with

excess of oxygen in a constant volume system, 22.3 kJ of heat is given out.

Calculate H for the combustion process. (R=8.31 J K-1 mol-1) (3 ma r ks)
Q.28 Account for the following :

(i) Of the lanthanide’s, cerium (atomic number 58) forms tetrapositive ion,

Ce4+ in aqueous solutions.

(ii) Transition metals have high enthalpy of atomisation.

(iii) Scandium forms no coloured ions and yet it is regarded as a transition

element. (3 m ar ks )

Q.29 Explain giving reason for each of the following :

(i) Chloroaceticacid has higher pKa value than acetic acid.

(ii) Carboxylic acid have higher boiling points than the alcohol’s of comparable

molecular masses.

(iii) Electrophilic substitution in benzoic acid takes places at meta position.(3

mar ks )

Q.30 (i) Explain the meaning of the statement, “Absorption is a surface


(ii) State two features of chemical adsorption which are not found with

physical adsorption. ( 3 ma r ks)

Q.31 (i) What is photosynthesis? Where does it occur in plants?

(ii) Name two products of photosynthesis which are required for the survival of

most of the chemotrophs. (3 m ar ks )

Q.32 Complete the following nuclear reactions :
    96              97
(i)    42Mo(…..,n) 43Tc
(ii) ……….( , 2n)      85At
      246      12             1
(iii)     96 +    6 –> …… + 4( 0n) (3 m ar ks )

Q.33 (a) Account for the following :

(i) Haloalkanes are more reactive than haloarenes.

(ii) Phenols are acidic in nature.

(iii) Unlike phenols, alcohol’s are easily protonated.

(b) Write the reactions involved in the preparation of :
(i) 1, 2-ethanediol from ethene, and

(ii) iodoform from 2-propanol (5 m ar ks )

Q.3 4 Present a comparative account of the following :

(i) Physical states of nitrogen and phosphorus.

(ii) Maximum covalency numbers of oxygen and sulphur.

(iii) Bond energies of F2 and Cl2.

(iv) Structures of chlorides of boron and aluminium.

(v) Proton affinities of NH3 and PH3 (5 m ar ks )

CBS E C hemi str y S am ple Que stion P aper
- Yea r 1998

Filed under:

    •   Class XII
    •   Chemistry

          Chemis tr y C las s - XII (CB SE )
        You ar e on Set no 1 Q.No . 1 to 20

Time allowed : 3 hours
Maximum Marks : 70

Gene r al Ins tr uction s :

(i) All questions are compulsory.
(ii) Marks for each question are indicated
against it.
(iii) Question number 1 to 10 are very short-
answer questions each of 1 mark. Answer
them in about one sentence each.
(iv) Question number 11 to 26 are short-
answer questions of 2 marks. Answer them in
not more than 30 words each.
(v) Question number 27 to 32 are short-
answer questions of 3 marks. Answer them in
not more than 40 words each.
(vi) Question number 33 to 34 are long-
answer questions of 5 marks each. Answer
them in not more than 70 words each.
(vii) Use Log tables, if necessary.
(viii) Please write down the serial number of
the question before attempting it.

Q1) Write the MO electronic configuration of
a diatomic molecule having a bond order of
three ? (Ma r ks 1)

Q2) What are non-stoichiometric
compounds ? (Mar ks 1)

Q3) Complete the nuclear reaction
expression ? (Ma r ks 1)

20   Co59 (d,p)……

Q4) Write the IUPAC name of (Ma r ks 1)

Image no.1

Q5 ) Why do noble gases form compounds
with fluorine and oxygen only ? (Mar ks 1)

Q6 ) Why is hydrochloric acid not used to
acidify a permanganate solution in volumetric
estimations of Fe2+ or C2O42-? (Ma r ks 1)
Q7 ) How many isomers are there for the
complex [Co(NH3)4 Cl2]Cl? (Mar ks 1)

Q8) Why are carbohydrates generally
optically active? (Mar ks 1)

Q9 ) Give one important use of each of the
following in pharmacy : (Ma r ks 1)
(i) Equanil
(ii) Morphine

Q10) Illustrate the function of mordent’s by
one example. ( Mar ks 1)

Q1 1) Predict the structure of MgO crystal
and co-ordination number of its cation in
which the cation and anion radii are equal to
65 pm and 140 pm respectively. (Mar ks 2 )

Q12) With the help of suitable diagrams,
illustrate the two types of non-ideal
solutions. (Mar ks 2 )

Q13) What is meant by average bond energy?
In what way is it different from bond energy
of a diatomic molecule ? Give suitable
examples. (Mar ks 2 )

Q14) Explain Kohlrausch’s law of
independent migration of ions. Mention one
application of Kohlrausch’s law. (Mar ks 2 )

Q1 5) For what concentration of Ag+ (aq) will
the e.m.f. of the given cell be zero at 25oC, if
concentration of Cu2+ (aq) is 0.1 M? (Mar ks
CU (s) | Cu2+ (0.1 M) || Ag+ (aq) | Ag (s)

[ Given Eo Ag+/Ag = + 0.80 V; Eo Cu2+/Cu = + 0.34 V ]

Q1 6) (a) Show graphically how the rate of a
first order reaction with only one reactant
depends upon the concentration of the
(b) Give one example of a first order reaction.
(Mar ks 2 )

Q1 7) For a reaction, the energy of activation
is zero. What is the value of rate constant at
300 K, if k = 1.6 x 106 s-1 at 280 K ? [ R = 8.31
JK-1 mol-3 ] (Mar ks 2 )

Q18) 1.0 x 10-6 g of radioactive iodine is
injected into the blood of a patient. How long
will it take for radioactivity to fall to 10% of
the initial value?
[ Given t1/2 for 53I133 = 8.05 days ] (Ma r ks 2)

Q1 9) Account for the following :
(i) Formaldehyde gives Cannizaro’s reaction
whereas acetaldehyde does not.
(ii) Carboxylic acids do not give the
characteristic reactions of carbonyl group.
(Mar ks 2 )

Q20 ) How are the following conversions
carried out?
(i) Ethanoic acid to propanoic acid.
(ii) Ethanol to propanone.
Write reaction equations and conditions to
support your answer. (Mar ks 2 )

Q21) Give an example of each with
necessary reaction conditions :
(i) Sandmeyer’s reaction
(ii) Kharasch Effect (Ma r ks 2)

Q22 ) What is ‘inert pair effect’? Discuss the
oxidation states of Group 13 elements in
relation to this effect. (Ma r ks 2)

Q23 ) A co-ordination compound has the
formula CoCl3.4NH3. It does not liberate
ammonia but precipitates chloride ions as
silver chloride. Give the IUPAC name of the
complex and write its structure formula.
(Mar ks 2 )

Q24 ) Write the information asked for in the
following polymers :
(i) Bakelite : material used for preparation
(ii) Synthetic rubber : monomer unit
(iii) PVC : monomer unit
(iv) Nylon-66 : materials required for
preparation. (Mar ks 1)

Q25) “The two strands of DNA are not
identical but are complementary.” Explain
this statement. ( Mar ks 2 )
Q26) Write the structure of adenosine
triphosphate indicating clearly the energy
rich bonds. How does this molecule form the
source of energy? (Ma r ks 2)

Q27) Explain how an electron can be
considered to have a particle as well as
nature. A moving electron has 4.9 x 10-25
joules of kinetic energy. Find out its De
Broglie wavelength.
(Given h = 6.6x10-34 Js; m = 9.1x10-31 kg)
(Mar ks 3 )

Q28 ) An aqueous solution freezes at 272.4 k,
while pure water freezes at 273.0 K.
Determine :
(i) the molality of the solution,
(ii) boiling point of the solution,
(iii) lowering of vapour pressure of water at
[ Given Kf = 1.86 K kg mol-, Kb = 0.512 K kg mol-1 and
vapour pressure of water at 298 K = 23.756 mm Hg ] (Mar ks 3)

Q29 ) (a) When NH NO (s) decomposes at 373 K, it forms N (g) and H O(g).
                  4    2                                  2          2
The H for the reaction at one atmosphere pressure and 373k is -223.6 kJ mol-1

of NH NO (s) decomposed. What is the value of E for the reaction under the
     4  4
same conditions?

[ Given R = 8.31 JK- mol-1 ]

(b) Account for the fact that E is numerically bigger H in the above case.

(Mar ks 3)

Q30) What is meant by the colloidal state of matter? Explain the following

terms :
(i) Multi-molecular colloids

(ii) Elector-dialysis (Ma r ks 3 )

Q31 ) An organic compound A having molecular formula, C H O give a
                                                         6 6
characteristic colour with aqueous FeCl solution. A on treatment with CO
                                       3                                 2
and NaOH at 400 K under pressure gives B which on acidification gives a

compund C. C reacts with acetyl chloride to give D which is a popular pain-

killer. Deduce the structures of A, B, C and D (Ma r ks 3 )

Q32 ) (a) Write the balanced equations for the following reactions :

450 K

(i) BF3 + LiH

(ii) NH3 + NaOCl

(iii) SiCl4 + H2O

(iv) XeF6 + KF

(b) State the reason for the occurrence of “diagonal relationship” in the

periodic table. ( Ma r ks 3)

Q33 ) (a) Write the general formula for nitroalkanes and for alkyl nitrites.

(b) How are nitroalkanes prepared alkanes?

© What happens when :

(i) nitroethane is treated with lithium aluminium hydride,

(ii) nitrobenzene is reduced with hydrogen using copper oxide as catalyst.

(d) Write two use of nitroalkanes, one each in the laboratory and in the

industry. (Mar ks 5)

Q34) (a) (i) What are inner transition elements? Write their general electronic


(ii) In what way are the observed oxidation states of the lanthanide’s related to

their electronic configuration?

(b) Describe the general characteristics of the transition elements with special

reference to their tendency to :

(i) exhibit paramagnetism,
(ii) form complex compounds,

(iii) their catalytic behaviour. (Mar ks 5)

CBS E C hemi str y S am ple Que stion P aper
- Yea r 199 7

Filed under:

    •   Class XII
    •   Chemistry

       Chemis tr y C las s - XII (CB SE )
   You ar e on qu es tions 1 t o 2 0 of Se t I

Q.1 State the physical significance of 2. (1
mar k)

Q.2 Write which one out of O+2 and O–2 is
more stable? (1 m ar k)

Q.3 Write an expression in the form of a
chemical equation for standard enthalpy of
formation of for CO? (1 m ar k)

Q.4 Write an expression to relate molar
conductivity of an electrotype to its degree
of dissociation? (1 m ar k)

Q.5 What is the ‘ambident group’ ? Give an
example. (1 m ar k)

Q.6 Indicate a chemical reaction involving a
homogeneous catalyst ? (1 m ar k)

Q.7 Mention two main function of
carbohydrates in plants ? (1 ma r k)

Q.8 How many sigma bonds are present in 3-
methylphenol ?(1 m ar k)

Q.9 Mention the chief reason for the
resemblance between beryllium and
aluminium ? (1 ma r k)

Q.10 Mention two important uses of
sulphuric acid ? (1 ma r k)

Q.11 What is energetically achieved by
coupling reaction in biological system?
Explain. (1 ma r k)

Q.12 What types of substance generally
constitute a chemical propellant? Briefly
describe the function of rocket propellant. (2
mar ks)

Q.13 The ionisation energy of hydrogen atom
is 1.312x106 J mol-1. Calculate the energy
required to excite the electron in a hydrogen
atom from the ground state to the first
excited state. (Avagadro constant=6.022x1023
mol-1)(2 m ar ks)

Q.14 Describe briefly two important function
of nucleic acid. ( 2 ma r ks)

Q.15 Calculate the free energy change when
one mole of sodium chloride is dissolve in
water at 298K.
(Given : Lattice energy of NaCl= -777.8 kj
mol-1, Hydration energy of NaCl= -774.1kj
mol-1 and S at 298 K = 0.043 K-1mol-1. (1
mar k)

Q.16 For the equilibrium PCl5(g) < ===> PCl5(g)
+ Cl2(g) at 298 K, K=1.8x10-7. Calculate Go for
the reaction. (R=8.314JK-1mol-1). (1 ma r k)

Q.17 The freezing point of pure nitrobenzene
is 278.8 K. When 2.5gm of an unknown
substance is dissolve in 100gm of
nitrobenzene, the freezing point of the
solution is found to be 276.8K. If the freezing
point depression constant of nitrobenzene is
8.0K Kg mol-1, what is the molar mass of
unknown substance? ( 2 ma r ks)

Q.18 For the reaction, 2A+2B+C—–> A2B+C,
rate law has been determined to be: rate =
k[A][B]2. If the rate constant, k = 2.0x10-6 mol-
6 2
 L and [C]=0.8 mol L-1? (2 marks)

Q.19 For the reaction NO2(g)+ CO(g)—–>CO2(g)
+ NO(g) the approximately determined rate
expression below 400K is rate = k[NO]2 what
mechanism can be proposed for above
reaction. (2 m ar ks)

Q.2 0 write IUPAC name of the following
compounds :
(i) (CH3)3C.CH2.CH2Cl
(ii) CH3.CH.CH.CH.CHO (2 ma r ks )

Q.21 Explain the mechanism of the acid-
catalysed dehydration of ethanol at high
temperature. ( 2 ma r ks)

Q.2 2 Comment on the structural difference
between thermoplastics and thermosetting
polymers. (2 ma r ks )

Q.2 3 What are micels? Given an example of
a micellar system. (2 ma r ks )

Q.2 4 Consider the given standard potentials
(in volts)in 1 M acidic solution :
Fe2+/Fe, -0.4 V ; Fe3+/Fe2+, +0.8 V
Mn2+/Mn, -1.2 V ; Mn3+/Mn2+, +1.5 V
(i) Comment on the relative stabilities of +2
and +3 oxidation states of iron and
(ii) Which of the two metals may be more
easily oxidised to +2 state?(2 m ar ks)

Q.25 Account for the following statements :
(2 ma r ks )
(i) Co(II) is stable in aqueous solution but in
the presence of strong ligands and air it can
get oxidised to Co(III). (Atomic number
(ii) One among the lanthanide’s,Ce(III) can be
easily oxidised to Ce(IV). (Atomic No :
Q.26 Write an equation in ionic form to
represent the oxidising action of Cr2O2-7 in
acidic medium. Also draw the structure of
Cr2O2-7. (2 m ar ks)

Q.27 An element of atomic mass 98.5g mol-1
occurs in fcc structure. If its unit cell edge
length is 500pm and its density is 5.22g cm-3,
what is the value of Avagadro Constant? (3
mar ks)

Q.2 8 One litre aqueous solution of sucrose
(molar mass=342g mol-1) weighing 1015g is
found to record an osmotic pressure of 4.82
atom at 293k. What is the molarity of the
sucrose solution? (R=0.0821 atom mol-1K-1)(3
mar ks)

Q.29 Calculate the potential of the following
cell reaction at 298K :
Sn4+(1.50M) + Zn(s) —> Sn2+(0.50M) +
The standard potential Eo of the cell is 0.89
V. Whether the potential of the cell will
increase or decrease, if the concentration of
Sn4+ is increased in the cell? (R = 8.314JK-1
mol-1; F=96,500 C mol-1) (3 ma r ks )

Q.3 0 (a) How many b -particles are emitted
in the decay series :
    U92 —> 206 Pb82 ?
(b) Complete the following nuclear reaction :
(i)2713 Al + 42 H –> 3015 Pb + …..
(ii)23592 U +   1
                    0   n –>   140
                                     56   +…..+ 210n (3 m ar ks)

Q.31 How are the following conversions
accomplished? (Write reaction only)
(i) Aniline to Chloro-benzine
(ii) Nitrobenzene to phenol
(iii) Aniline to benzoic acid (3 ma r ks )

Q.3 2 Select the complex formation reaction
and write an expression for the stability
constant of the complex species. What
information is conveyed regarding the
strength of ligands from the stability
constant values of their complexes with a
metal ion? Illustrate your answer with
example of monodentic ligands. (3 ma r ks )

Q.3 3 (a) Explain giving reason each of he
following :
(i) CCl4 remains unaffected whereas SiCl4 is
easily hydrolysed by water.
(ii) Nitrogen exists as a diatomic molecule,
N2, whereas phosphorus exists as tetra-
atomic molecule, P4.
(iii) SF6 is known but SH6 not known.
(b) Write the balance equation fro the
following reaction :
(i) B2H6 + LiH —>
(ii) BrO3 + F2 + OH—-> (5 m ar ks )

Q.3 4 (a)You are provided with 4 reagent :
LiAlH4, I2/NaOH, NaHSO3 and Sciff’s reagent.
Write which two reagents can be used to
distinguish between the compounds in each
of the following pairs :
(i) CH3CHO and CH3COCH3
(ii) CH3CHO and C6H5CHO
(iii) C6H5COCH3 and C6H5COCH3 and
(b) Account for the following :
(i) The order of reactivity of halogen acids
with ether is HI > HBr > HCl
(ii) The pKa value of choloroacetic acid is
lower than the pKa value of acetic acid. (5
mar ks)

Shared By: