Activation energy for the acid catalysed hydrolysis of
sucrose is 6.22k3 .
While the activation energy is only 2.15kJwhen
hydrolysis is catalysed by the enzyme inverts. Explain, [1]
Explain as to why haloarenes are much less reactive than
haloalkanes towards nucleophilic substitution
reactions. [2]
Or
Which compound in each of the following pairs will react
faster in reaction
with?OH? Why?
(i) (ii)
Give chemical reactions in support of the following
observations.
(i) Sulphuric acid has low volatility.
(ii) Iodide ions can be oxidised by oxygen in acidic
medium, [1+1]
(i) Why do the transition elements exhibit higher
enthalpies of atomization?
(ii) In the series Sc (Z = 21) to Zn (Z = 30) the enthalpy
of atomization of zinc is the lowest i.e., 126 kJ .
Why? [1+1]
Resistance of a conductivity cell filled with 0.1 mol KCl
solution is . If
the resistance of the same cell when filled with 0.02 mol KCl
solution is .calculate
the conductivity and molar conductivity of 0.02 mol KCl
solution.
The conductivity of 0.1 mol KCl
solution is 1.29 S/m.
Copper crystallises with face centred cubic unit cell. If
the radius of copper atom is 127.8 pm, calculate the density of copper metal.
(Atomic mass of Cu = 63.55 u and Avogadro's number ) [3]
Or
Iron has a body centred cubic unit cell with the cell
dimension of 286.65 pm. Density of iron is 7.87 g . Use
this information to calculate Avogadro's number. (Atomic mass of Fe = 56.0
u) [3]
Humans, monkeys and guinea pigs do not have the enzymes
necessary for the biosynthesis of vitamin C, so they must include the vitamin
in their diets. It is also required for the synthesis of collagen, which is the
structural protein of skin, tenders, connective tissue and bone.
Answer the following questions based on above passage.
(a) Write structure of vitamin C and the functional groups
therein. [1]
(b) Is it acidic in nature? What is the common name of
vitamin C? [1]
(c) What is the oxidation product of vitamin
C? [1]
2 g of benzoic acid dissolved
in 25 g of benzene shows a depression in freezing point equal to 1.62 K. Molar
depression constant for benzene is 4.9 K kg . What
is the percentage association of acid if it forms dimer in solution?
[3]
(a) Give one main difference between lyophilic and
lyophobic colloids.
(b) Explain.
(i) Sky appears blue in colour.
(ii) A freshly formed precipitate of ferric hydroxide can
be converted to a colloidal sol by shaking it with a small quantity of ferric
chloride. [1+2]
Give chemical equations for the following reactions.
(i) Oxidation of nitrite ion by in
acidic medium.
(ii) Acidification of potassium dichromate solution.
(iii) Disproportionate of manganese ion in acidic
solution. [3x1]
(i) State the hybridisation and magnetic behaviour of . (Atomic
number of Cr is 24)
(ii) Which of the two is more stable and why?or
(iii) What are the various factors affecting crystal field
splitting energy? [3
x 1]
(a) Why can't alumina be reduced by carbon?
(b) What is the role of depressant in froth floatation
process?
(c) Co which is better reducing agent for FeO?
(i) In the lower part of blast furnace (higher
temperature)
(ii) In the upper part of blast furnace (lower
temperature) [3
x 1]
The following results have been obtained during the kinetic studies of the reaction,
Experiment
Initial rate of formation of
0.1
0.3
0.3
0.4
0.1
0.2
0.4
0.1
Determine the rate law and the rate constant for the reaction. [5]
Or
(a) With the help, of an example, explain what is meant by pseudo first order reaction? [2]
(b) The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature. [3]
(a) An orange solid (A) on heating gives a colourless gas
(5). The gas (B) in dry condition is passed over heated Ca to give a solid (C).
The solid (C) further reacts with water to produce gas (C) which forms a blue
coloured compound (£) on reaction with copper sulphate solution. Identify A, B,
C, D, E and give the sequence of reactions involved.
[3]
(b) Arrange the following in the order of property
indicated for each set.
(i) HCl, HBr, HI, HF. Decreasing thermal stability.
(ii) Xe, He, Kr, Rn, Ne. Decreasing order of electron gain
enthalpy. [2]
Or
(a) Give reason
(i) Solid is an
ionic compound. (ii) Ozone is thermodynamically
unstable.
(iii) Most of the reactions of fluorine are exothermic.
(b) Draw the structures of the following.
(i)
(ii)
[3+2]
(a) Give plausible explanation for each of the following.
(i) Cyclohexanone forms cyanohydrins in good yield but
2,2,6-trimethyl cyclohexanone does not.
(ii) These are two ?NH^ groups in semicarbazide. However
only one is involved in the formation of semicarbazones.
(iii) During the preparation of esters from a carboxylic
acid and an alcohol in the presence of an acid catalyst, the water or the ester
should be removed as soon as it is formed.
(b) Write structural formulas and names of four possible
aldol condensation product from propanal and
butanal. [3+2]
Or
(a) How will you bring about the following conversions in
not more than two steps?
(i) Benzaldehyde to 3-phenyl propan-1-ol.
(ii) Benzoic acid to m-nitrobenzyl alcohol.
(iii) Propanone to propene.
(b) Describe the following.
(i) Cross aldol condensation (ii) Decarboxylation [3+2]