|Course Code :||CHE-01|
|Course Title :||Atoms and Molecules|
|Medium :||English Medium|
|Session :||July 2020 and January 2021 (2020-21)|
|Max Marks :||100|
|Submission Period :||From 1st January, 2021 to 31st December, 2021|
|Solution Type :||Softcopy (PDF File)|
Tutor Marked Assignment
CHE-01: Atoms and Molecules
Course Code: CHE-01
Assignment Code; CHE-01/TMA/2021
Maximum Marks: 100
Each question carries 10 marks
Use the following data
Permittivity in vacuum = 8.854 × 10-12 C2N-1m-2
Planck’s constant = 6.626 × 10-34 J s
Mass of electron = 9.109 × 10-31 kg
Magnitude of the charge on the electron = 1.602 × 10-19 C
Avogadro constant = 6.022 × 1023 mol-1
Velocity of light = 2.998 × 108 m s-1
Relative atomic masses: Hydrogen = 1; Deuterium = 2; Iodine = 127
1. a) Calculate the radius of the second and third orbits in He+ ion. Also calculate the energy of the electron in the second and third orbits of He+ ion. (5)
Hint: Use Bohr atom model. Z value for He+ ion = 2.
b) Calculate he wave number (m-1) and energy (kJ mol)-1 of the light of wavelength 800nm. (5)
2. a) Write the values of four quantum numbers for 4s and 4p electrons. (5)
b) Calculate the de Broglie wavelength associated with a body of mass 1.5 kg moving with a velocity of 100 m s-1. (5)
3.a) Arrive at the Lewis structures of ICI+2 and ICI–2 ions. Using VSEPR theory, predict the shapes of these compounds. (5)
b) Calculate the bond lengths in bromoethane and bromoethylene using covalent radii values given in Table 3.10 of Unit 3. For hydrogen, assume that the covalent radius in 28 pm in these compounds. (5)
4. a) Explain the structure of BF3 molecule based on hybridization concept. What is its shape? (5)
b) Starting from Lewis structures, determine the hybridisation type of the central atoms in IF+4 and ICI–4. (5)
5. a) State the definitions of bonding, antibonding and nonbonding orbitals. Draw the molecular orbitals obtained by the linear combination of two 1s orbitals. (5)
b) Using the molecular orbital theory, explain why the oxygen-to-oxygen bond is stronger in oxygen molecule than in peroxide (O2-2) ion. (5)
Hint: Start from molecular orbital configuration for oxygen molecule and peroxide
Ion; then calculate bond order for each.
6. a) An element X forms a compound, XOCl3, in which X and O form a double bond while X and Cl form single bonds. Identify X from the following elements:
i) Al ii) Si iii) P (iv) S.
Give reason for your answer. Predict the shape of the molecule. (5)
b) You are given a gaseous substance. Suggest an experimental method to find out whether it is polar or nonpolar. Discuss the steps to be used in this method. (5)
7. a) (Fe(CN)6)3- is a low-spin complex ion while (Fe(H2O)6)3+ is a high-spin complex ion. Both the complex ions are derived from ferric (Fe(III)) ion. Following the example worked out for d4 configuration in Sec. 6.8 of Unit 6, answer the following:
i) What is the number of electron in 3d level of Fe3+ ion?
ii) Indicate the number of unpaired electrons in 3d level of Fe (III) species in each of the complex ions. Predict the magnetic moments of both the complex ions in Bohr magnetion units. (5)
b) Explain the terms, racemic mixture and meso form, with an example in each case. Mention a difference between the two. (5)
8. a) The bond length of HI molecule is 163 pm. Calculate its (i) moment of inertia and (ii) rotational constant. (5)
b) What is the essential condition for a molecule to be microwave active? Give three examples each for the diatomic molecules. (5)
i) having microwave activity and
ii) not having microwave activity.
9. a) Calculate the ratio for the fundamental frequencies of HI and DI. (5)
b) Based on Beer-Lambert law, explain the method of finding out the concentration of a given solution of potassium dichromate. You are also provided with a standard solution of potassium dichromate. (5)
10. a) The rate constant for the radioactive disintegration of 6027Co is 0.1317 year-1.
Calculate the mass of 6027Co that will remain after 21.04 years out of 1 gram sample. (5)
b) Explain the principle of determining the age of organic materials using radioactive dating method. (5)
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