Download Assignment CHE-04 TMA-01,02 Year 2005

CHE-04
Assignment Booklet
Bachelor’s Degree Programme (B. Sc.)
Physical Chemistry
School of Sciences
Indira Gandhi National Open University
New Delhi
2005 - 2006
1
Dear Student,
We hope you are familiar with the system of evaluation to be followed for the Bachelor’s
Degree Programme.
A weightage of 30 percent, as you are aware, has been earmarked for continuous evaluation.
This would consist of two tutor-marked assignments (TMA-1 and TMA-2) for CHE - 04
Course. You can find both these assignments in this booklet. TMA-1 is based on Blocks 1 and
2 and, TMA-2 is based on Blocks 3, 4 and 5 of CHE-04 course.
Instructions for Formating Your Assignments
Before attempting the assignment, please read the following instructions carefully.
1. On top of the first page of each TMA answer sheet, please write the details exactly in the
following format:
Enrolment No : .......................……………
Name
: ........................…………….
Address
: ........................…………….
Course Code : ........................……………
…...………………………..
Course Title
…………………………….
: .......................…………….
Assignment No : ......................…………….
Study Centre : ............................................
Date
: ………...........................…..
(Name and Code)
PLEASE FOLLOW THE ABOVE FORMAT STRICTLY TO FACILITATE
EVALUATION AND TO AVOID DELAY.
2. Use only foolscap size writing paper (but not of very thin variety) for writing your answers.
3. Leave 4 cm margin on the left, top and bottom of your answer sheet.
4. Your answers should be precise.
5. While writing answers, clearly indicate the question number along with the part being
solved.
6. These assignments are to be submitted as follows:

First assignment to be submitted to the Study Centre Coordinator within 6 weeks of
receiving this booklet.

Second assignment to be submitted to the Study Centre Coordinator within 12 weeks
of receiving this booklet.
We strongly suggest that you should retain a copy of your assignment.
Wishing you all good luck.
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Tutor Marked Assignment – 1
Course Code : CHE – 04
Assignment Code : CHE – 04/TMA-1/2005-06
Maximum Marks : 100
Answer all questions. For the values of physical constants, consult the study materials.
1. The molar mass of carbon monoxide molecule is 28 grams. If its root mean square
speed is 6.00×104 cm s─1, calculate its (i) translational energy per molecule,
(ii) translational energy per mole, (iii) temperature and (iv) rotational energy per mole.
Express your answers in SI units.
(3+2+3+2)
2. If 8.0×10─3 kg of helium gas and 6.4×10─2 kg of sulphur dioxide gas are taken at
3.00×102 K in a vessel at a total pressure of 6×105 Pa, calculate the partial pressures
of the two gases. Also calculate the volume of the vessel and the concentration of
each gas (in molarity unit).
(4+2+4)
3. (a) Calculate the mean free path of a gas at 3.00×102 K and 1.0×105 Pa pressure,
if collision diameter is 3.780×10─10 m.
(5)
(b) Arrange each of the following pairs of compounds in the increasing order of
boiling points and also state the reason:
(i) Propane and methanol
(ii) Chlorine and bromine
(iii) Pentane and 2,2 – dimethylpropane
(5)
4. For nitrogen gas, the van der Waals constant, a, has the value 0.1408 Pa m6 mol─2.
At 298.2 K, 1 mol of nitrogen gas is kept in a vessel of volume 4.894×10─2.m3.
(i) Calculate pressure of the gas, assuming ideal behaviour. (ii) Assuming that the
gas obeys van der Waals equation and that the van der Waals constant, b, is
negligibly small, calculate the pressure of the gas and compressibility factor, z.
(3+4+3)
5. (a) Using diagrams, explain the shapes of meniscus of
(i) water in a glass tube and (ii) mercury in a glass tube.
6.
(4)
(b) Explain the effect of hydrogen bonding and metallic bonding on the surface
tension values of liquids. Give an example for each case.
(4)
(c) Explain the difference between the structures of a single crystal and a smectic
liquid crystal
(2)
(a) Nickel has a fcc lattice and its cell-edge length is 3.524×10─10 m. Calculate the
distance between its (111) planes. What would be the angle of incidence at which
first order reflection would occur from the (111) planes, if the wavelength of X-rays
used is 154 pm?
(5)
(b) Using diagrams, (i) explain the basic difference between the fcc structure of a
metallic crystal lattice and fcc structure of an ionic crystal lattice and (ii) derive
the value of net atom(s) or formula unit(s) per unit cell in each case.
3
(5)
7. 50 mol of a monoatomic ideal gas occupies a volume of 0.8314 m3 at 1.50×105 Pa
and 3.00×102 K. The gas undergoes expansion and the final pressure is 7.50×104 Pa.
Calculate the final volume of the gas, assuming that it proceeds through
(i) reversible isothermal process and (ii) reversible adiabatic process. Also
calculate the maximum work available (-W) through isothermal reversible
expansion mentioned above. The molar heat capacity of monoatomic gas at
constant volume = = 12.47 J mol─1 K─1.
(2+5+3)
8. (a) Using Table 7.1 of Unit 7, attempt the following: (i) Calculate the standard
enthalpy of combustion of C6H6(l ) at 298.15K. (ii) Also if the standard enthalpy
of formation of C2H2(g) is 223.2 kJ mol─1, calculate the standard enthalpy
change accompanying the conversion of C2H2(g) into C6H6(l).
(4+3)
(b) Calculate the enthalpy of formation of HF(g) using Table 7.2 of Unit 7 for the bond
enthalpies of H – H, F – F and H – F bonds.
(3)
9. (a) Calculate the standard entropy change, when 2 mol of an ideal gas undergoes
expansion as per the following data :
Physical parameter
Initial value
Final value
Temperature
3.00×102 K
3.50×102 K
Volume
5.00×10─3 m3
5.00×10─2 m3
Molar heat capacity of the gas at constant volume = 12.47 J mol─1 K─1.
(b)
(5)
Urea undergoes hydrolysis to give ammonia and carbon dioxide according to the
following equation:
CO(NH2)2 (s) + H2O(l) → CO2 (g) + 2NH3 (g)
Calculate the standard entropy change for this reaction at 298.15 K, if 2 mol of urea
undergoes hydrolysis. Use the following data:
Substance
Standard entropy/ J mol─1 K─1
Urea
174.5
Water
69.9
Carbon dioxide
213.7
Ammonia
193.2
(5)
10. (a) Calculate the boiling point of water at a pressure of 1.00×104 Pa. The molar
enthalpy of vaporisation of water is 4.10×104 J mol─1. The boiling point of water
at 1.00×105 Pa is 373 K.
(5)
(b) Calculate the change in Gibbs free energy when 2.00 mol of an ideal gas expands
reversibly and isothermally at 4.00×102 K such that its volume increases two fold.
comment on the spontaneity of the process.
(5)
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Tutor Marked Assignment – 2
Course Code : CHE – 04
Assignment Code : CHE – 04/TMA-2/2005-06
Maximum Marks : 100
Answer all questions. For the values of physical constants, consult the study materials.
1. (a) The Henry’s law constant for N2 at 298 K is 8.68×109 Pa. Calculate the mass of
nitrogen that could be dissolved in 1 kg of water at 298 K, if the partial pressure of
nitrogen over the aqueous solution is 8.0×104 Pa.
(5)
(b) The normal boiling points of CCl4 and CH3OH are 349.9 K and 337.8 K. These two
liquids form azeotrope which boils at 328.8 K with 79.44% of CCl4. Draw boiling
point – composition diagram for this system and explain the effect of repeated
distillation and condensation of a liquid mixture containing 90% of CCl4 by mass. (5)
2. (a) Explain the procedure that can be followed to establish that a particular solute forms
a dimer in an organic solvent that is immiscible with water. Use equation 11.21of
Unit 11 and graphical method.
(5)
(b) State the significance of the following terms:
(i) Chemical actinometers
(ii) Thermal dissociation energy
(iii) Flash photolysis
(iv) Phosphorescence
(v) Sensitised fluorescence
(5)
3. (a) Sodium chloride is 90% dissociated in a solution. Calculate the van’t Hoff factor
and the elevation in boiling point of a solution prepared by dissolving 1.169×10-3 kg
of sodium chloride in 0.100 kg of water.
(5)
(b) State the two conditions under which deviations from Langmuir adsorption isotherm
are observed. Explain the terms, auto-catalysis and inhibition of the catalyst, giving
an example in each case.
(5)
4. Zinc and cadmium constitute a simple eutectic system. The melting points of zinc and
cadmium are 692 K and 596 K, respectively. The eutectic temperature is 543 K. The
eutectic composition is 17% by weight zinc. (i) Using diagrams for cooling curves,
explain the method of constructing the phase diagram of zinc-cadmium system.
(ii) Draw the phase diagram of zinc - cadmium system on a rough scale and mark the
stable phases in various regions. Explain the changes that would occur if the melt
containing 50% by weight zinc is cooled.
(10)
5. (a) At a particular temperature, a mixture of 2 mol each of hydrogen gas and iodine
vapour was introduced into a flask of volume 1 dm3. On the attainment of the
equilibrium, the concentration of each of these two components was found to
be 0.4 M. The temperature was maintained constant. Find the equilibrium
constant for the formation of hydrogen iodide.
5
(4)
(b)Predict the effect of increase of pressure on the following equilibria:
(i) 2NO(g) + Cl2(g) → 2NOCl(g)
(ii) N2(g) + O2(g) → 2NO(g)
(2+2)
(c) Predict the effect of increase of temperature on the following equilibrium:
2CO(g) + O2(g) → 2CO2(g) + 567.8 kJ
(2)
6. (a) The solubility product for Fe(OH)3 at 298 K is 2.0×10─39.Calculate the solubility
of Fe(OH)3 (i) in water and (ii) in presence of 0.1 M sodium hydroxide solution.
(b) At 298 K, calculate the ratio of [CH3COOH]/[CH3COONa] required to produce
a pH of 4.20. Ka for CH3COOH is 1.8×10─5.
(5)
(5)
7. (a) Discuss the steps involved in determining the dissociation constant of ammonium
hydroxide using conductivity measurements. Assume that necessary chemicals and
instrument are available. You are given a conductance cell of unknown cell constant. (5)
(b) At 298 K, ionic conductance values at infinite dilution for silver ion and nitrate ion
are 61.9×10─4 S m2 mol─1 and 71.5×10─4 S m2 mol─1, respectively. Calculate (i) the
transport number and (ii) the ionic mobility of silver ion and nitrate ion in an
infinitely dilute solution of AgNO3.
(5)
8
(a) State the steps involved in the determination of ∆G, ∆S and ∆H using emf
measurements for the reaction in which chlorine gas displaces bromine liquid
from an aqueous solution containing bromide ions.
(5)
(b) Calculate the emf of the following cell at 298.15 K :
Zn(s) | Zn2+ (0.01 M) || Ag+(0.1 M) | Ag(s)
Use Table 17.1. Also calculate ∆G° for the cell reaction.
9
(5)
(a) At 300 K, the hydrolysis of benzene diazonium chloride in its aqueous solution is
a first order reaction. The first order rate constant for the reaction is 5.44×10─5 s─1.
Calculate the half life period for the reaction and time taken for 90% completion
of the reaction.
(5)
(b) In a chemical reaction undergone by the reactant, A, at a particular temperature,
the following data are obtained with respect to the values of its initial concentration
and the corresponding half life period:
[A]0/10─2 M
1.60
1.00
Half life period/s
250
400
Calculate the order of the reaction. Specify the units of the rate constant of the
reaction.
10 (i) Explain any three applications of colloids.
(ii) Explain Schulze-Hardy rule giving an example.
(iii) How can you distinguish between oil-in-water type emulsions from
water- in-oil type emulsions?
(iv) Explain the term, gold number.
6
(5)
(3+3+2+2)