Tutor Marked Assignment
Assignment Booklet
Bachelor’s Degree Programme (B. Sc.)
Atoms and Molecules
School of Sciences
Indira Gandhi National Open University
New Delhi
20002
Dear Student,
As explained in the programme guide for B.Sc. Programme, you will have to do one assignment for this elective course, Atoms and Molecules (CHE-01). This is a tutor marked assignment (TMA).
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Tutor Marked Assignment
Course Code : CHE –01
Assignment Code: CHE – 01/TMA/2002
Last Date for Submission of Assignment: Sep. 30, 2002
Total Marks: 100
Each question carries 10 marks.
Wherever required, use the table of physical constants and periodic table given at the end of Block – 1.
1. (a) Calculate the radius of the second orbit of Li2+ ion. Also calculate the velocity of the electron in the second orbit of Li2+ ion.
Hint: All ions having electronic configuration similar to hydrogen atom obey equations given in Sections 1.8 to 1.11 of Unit 1.
(b) Calculate (i) Rydberg constant for Be3+ constant and (ii) fourth ionisation energy of beryllium in J atom-1 and kJ mol-1 units
2. (a) (i) Indicate the n, l, ml and ms values for the electrons in 3p and 5s levels.
(ii) State the names of orbitals filled in the elements of the fourth period of the periodic table.
(b) Calculate the mass of He+ion in kg unit. If it moves with a velocity of 5´104 m s-1, calculate its de Broglie wavelength.
Hint: Assume that mass of He+ ion is equal to mass of He atom.
3. (a) Calculate the components of energy along x, y and z axes and the total energy for an electron in a cubical box of length 10-9 m, if nx = 3, ny = nz = 1. State the values of nx, ny and nx for two other energy states which are desenrate with this level.
Hint: Use the principle of calculation of energy of a particle in a three dimensional box.
(b) Draw a curve on a rough scale indicating the variation in ionisation energy values of third period elements using the data given in Table 3.3 of Unit 3. Explain the reasons for the rising and falling portions of the curve.
Hint: Do the sketch similar to Fig. 3.1 of Unit 3.
4. (a) Using the data given in Tables 3.5 and 3.6 of Unit 3 for K+ and Br- ions,
(i) find the radius ratio of K+ ion to Br- ion
(ii) predict the shape of crystal geometry of KBr
(iii) draw a diagram indicating the arrangement of K+ and Br- ions in the crystal.
(b) Write down Born – Haber cycle for the BaO crystal formation. Using it, obtain an equation useful in calculating lattice energy of BaO crystal.
5. (a) Draw Lewis structures of and ions. Predict the
(i) shapes of these ions using VSEPR theory and
(ii) hybridisation states of phosphorus atom in these two ions
(b) Predict the bond lengths the following molecule using hybridization concept and Table 4.4.
6. (a) Using molecular orbital theory, draw the energy patterns of the following
(i) B2
(ii) O2
Comment on the difference between the two patterns.
(b) The three resonance structures of the anion formed by the ionisation of potassium cyanate are given in Sec. 4.5 of Unit 4.
(i) Justify the charges indicated in each of its structures using the principles of ionic bonding and formal charges.
(ii) Write two possible representations for the following structure using a coordinate bond in each case.
7. (a) The dipole moment of HBr is 2.602´10-30 C m and its bond length is 141 pm. Calculate its percentage ionic character.
(b) (i) Nitrogen dioxide can exist as both monomer and dimmer. Based on magnetic characteristics, how can you differentiate between the two?
(ii) For 2, 3 – dichlorobutane, draw the structures for the enatiomers and meso forms.
8. (a) Label each of the following as microwave active or microwave inactive:
(i) CO2 (Linear)
(ii) SnCl2 (Angular)
(iii) BF3 (Trigonal planar)
(iv) XeF4 (Square planar)
(v) NH3 (Trigonal pyramidal)
State the reason in each case.
(b) The bond length of 1H127I molecule is 163 pm. Calculate
(i) moment of inertia and
(ii) rotational constant.
9. (a) For hydrogen iodide, 1H127I, force constant is 314 N m-1. Calculate the fundamental frequency in cm-1 unit for
(i) 1H127I
(ii) 2H128I
(b) (i) Calculate the number of vibrational degrees of freedom for hydrogen fluoride and chloroethene.
(ii) For a compound, molear extinction coefficient is 215 m2 mol-1 at 255 nm. What concentration of the compound in a solution will cause a 30% decrease in the intensity of 255 nm radiation? The cell thicken is 0.01m.
10. (a) Calculate in J and MeV units the binding energy per nucleus and binding energy per nucleon for
Mass of proton = 1.00728 u
Mass of neutron = 1.00867 u
Actual atomic mass of = 18.99840 u
1 u = 931.9 Mev nucleus-1
= 1.493´10-10 J nucleus-1
(b) The half life of a radioactive element is 1620 years. Calculate the radioactive decay constant. Out of 1 gram sample of the element, how much will remain after 4860 years?