Indira Gandhi National Open University (IGNOU) 2005 B.Sc Chemistry Atoms And Molecules - - Question Paper
CHE-1
BACHELOR OF SCIENCE (B.Sc.) Term-End Examination June, 2005
CHEMISTRY CHE-1 : ATOMS AND MOLECULES
Time : 1 hour Maximum Marks : 25
Note : Answer any two questions. Each question carries 12 marks.
1. (a) What is a black-body ? Give three main aspects of
black-body radiation. aX
*2
(b) State the meaning of the following terms
(i) node
(ii) matter waves
(iii) azimuthal quantum number
(iv) normalization constant
order of their ionic radii :
F", Na+, Mg2*, O2"
Give reason in support of your answer:
(ii) Predict the structure of BF3 molecule using VSEPR theory. (Atomic Nos. : B 5; F = 9). 4
2. (a) Give the type of hybridisation of all the carbon atoms in the following compounds :
4
(i) HCHO
(iii) H2C = CHCH - CH2
(b) Write the molecular orbital configuration of CO and calculate its bond order. Will it be paramagnetic ? (Atomic Nos. : C = 6; 0 = 8). 4
(c) Define dielectric constant. State the expression relating dielectric constant with the . total molar polarisation. State the significance of the terms
used.
1
3, (a) What type of energy changes occur in microwave active molecules when they are subjected to microwave radiation ?
(b) The lowest wave number absorption line in the rotational spectrum of *H 19F is at 4-111 x 103 m-1.
Answer the following questions : 3
(i) What is the value of lowest frequency of absorption in the rotational spectrum of HF ?
(ii) What are the two energy levels involved in this transition ?
(iii) What is the value of the rotational constant (B) for HF ? (Velocity of light = 3 0 x 1G8 ms-1).
(c) Write the expression for vibrational energy and state
the significance of the various terms used. Using it
obtain expressions useful in calculating the vibrational
energy for v =1 and v = 2 vibrational levels of a
diatomic molecule* Also explain the term, zero point
energy. 4I
2
(d) Explain any two of the following with the help of one example : 2+2
(i) Nuclear fusion
(ii) Nuclear fission (u\) Tracer technique
CHE-1 4
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