CHE-01 Atoms and Molecules Solved Assignment 2018

Description

CHE-01 ASSIGNMENT BOOKLET
Bachelor’s Degree Programme (B.Sc.)
ATOMS AND MOLECULES
(Valid from 1st January, 2018 to 31st December, 2018)

1. a) Describe the common features which can be explained by the theoretical model of Bohr? Briefly write the limitation of this model.
b) Calculate the ionization energy of hydrogen atom using Bohr’s theory.
2. a) Derive an expression for calculating energy values corresponding n = 3 for a particle in one dimensional box.
b) Write the values of four quantum numbers for 3d electrons.
3. a) Explain the reason for the variation of the first ionization energies of the third period elements.
b) Calculate the lattice energy (in Units kJ mol^-1) for ZnO crystal using Eq. 3.4 based on electrostatic model and using a Born-Haber cycle. Compare the two answers and comment on any difference.
Useful data:
Medelung constant (A) = 1.6411
Born Constant (n) = 8
Internuclear distance (a) = 199 pm
Zn(s) + ½ O₂(g) -> ZnO(s) ΔHf = -350.5 kJ mol^-1
Zn(s) -> Zn(g) ΔH_S = 130.4 kJ mol^-1
Zn(g) -> Zn⁺(g) I(Zn) = 906.3 kJ mol^-1
Zn⁺(s) -> Zn²⁺(g) I(Zn+) = 1733 kJ mol^-1
½ O₂(g) -> O(g) ½ΔH_d = 248.5 kJ mol^-1
O(g) -> O^–(g) EA(O) = 141 kJ mol^-1
O^–(g) -> O^2-(g) EA(O^–) = -780 kJ mol^-1
4. a) In carbonate ion, all the three C-O bonds have identical bond length. Explain.
b) Explain the type of hybridization in phosphorous pentafluoride.
5. a) By writing molecular orbital configuration for each of following molecules calculate the bond order and also determine whether it is paramagnetic or diamagnetic.
(i) NO (ii) CO (iii) O₂⁺
b) Using suitable examples define gerade and ungerade orbitals. (4)
6. a) The dipole moment of HBr is 2.60 x 10^-30 C m and interatomic distance 141 pm. What is the percentage ionic character of HBr?
b) Draw all of the stereoisomers of 2,3-butandiol, label meso compounds and pairs of enantiomer.
c) What is the predicted magnetic moment of Cu⁺ and Cu²⁺ ions in μB Unit (Atomic number of Cu 29)?
7. a) Given that the spacing of the lines in the microwave spectrum of ²⁴Al¹H is constant at 12.604 cm^-1. Calculate the moment of inertia and bond length of the molecule.
b) Determine the wavelength for a transition from the ν = 0 to the ν = 1 level. Is this transition in the IR region of the electromagnetic spectrum?
c) Which of the following molecules exhibit rotational and or vibrational spectra H₂, HF, CO, NO
(2)
8. a) From the infrared spectrum given below, identify the possible functional groups corresponding to the peaks indicated in the arrows.
b) Explain why ϖ -> ϖ* transitions are the most useful transition in UV-VIS spectroscopy?
c) UV-VIS absorption spectra are broad band spectra. Explain.
9. a) Normal water contains isotope of hydrogen ³H, tritium. It has a half-life of 12.3 years.
Determine the age of a bottle of wine whose ³H radiations is about 1/10 that present in new wine.
b) Complete following equations:
i) ³⁰P+ … ->³⁰Si
ii) ¹⁰B +n-> … α
iii) ²⁰Ne + ¹³⁶Ba -> ¹⁵⁰Dy + ….
iv) … + ² -> H ²²Na α
v) ²⁴¹Am + … -> ²⁴³Bk 2n
10. a) Arrive at the Lewis structure of XeF4 using the steps given in Unit 3.
b) Predict the hybridization state of each carbon atom in allene which has the following structure:
CH₂ = C = CH₂
c) Calculate the number of normal modes of vibration for the following compounds:
i) H₂O
CH₄
ii) HBr