Chem-DSE-1: Chemistry of Major and Minor Biogenic Elements — DU B. Sc. Life Science (Chemistry) Previous Year Question Papers

Chemistry of Major and Minor Biogenic Elements l. (a) Discuss the relationship between exchange pair of electrons and exchange energy With an example. (b) Write a short note on the structure and bonding of diborane. ( c) Arrange the following in the order of their acidic strength giving reason : ( d) The physical properties of benzene and borazine are quite similar but their chemical properties are different. Explain. (4,5,2,4) 2. (a) Explain why are atoms with half- filled and completely-filled orbitals stable? (b) Explain how the oxides of nitrogen affect the human health and environment. (c) Name and draw the structures of the following oxoacids of phosphorus : (d) Complete the following reactions : NH4Cl + excess PCl 5 3 • (a) Arrange the following ions in the increasing order of their size, giving reason : (b) Complete the following reactions : Give the colour of the product in reaction (iii). (c) Elements of group 16 show lower value of first ionisation energy compared to the elements in the corresponding periods of group 15. Explain. ( d) Why is the aromatic character of phosphazene less than that of benzene? (4 4 3 4) 4. (a) The ionisation of Mg to Mg2+ requires three times the energy as compared to Mg to Mg+ , but still the commonly existing ion is Mg2 (b) Write the names, formulae and structures of the five oxoacids of sulphur. ( d) What are the differences between silicone rubbers and normal rubbers? (4,5,2,4) 5. (a) Write a short note on crown ethers and cryptates, discussing their biological importance. (b) Arrange the following in increasing order of: (i) Reducing character - H3P03, H3P0 2, H3PO 4 (give reason) HC103 (give reason) (c) Write the formula and draw the structure of pyro silicates. Give examples of pyro silicate minerals. 6. (a) Discuss the importance of calcium in the biosystem. (b) Write the differences between alkanes and silanes. (c) What is Caro's Acid? How it is prepared? What is the role of chain stopping un 1ormation of silicone polymers. ive