1. Calculate the number of atoms in 4g of He.

2. Which quantum numbers originate from Schrodinger wave equation? 3. Which of the two is bigger in size and why? Cl or Cl- 4. What is the hybridization of central atom in following? NH3,C2 H4 5. What is the dipole moment of CCl4 molecule? Account for your answer. 6. Describe the hybridization in case of PCl5. Why are axial bonds longer as compared to the equatorial bonds? 7. Use the molecular orbital theory to explain why Be2 molecule does not exist. 8. Explain the formation of sigma and pi bonds in C2H4 with the help of diagram . 9.Mention the hybrid state of the two carbon atoms. 10. Calculate the concentrationof nitric acid in moles per litre in a sample which has density Of 1.41gmL-1 and the mass percentage of HNO3 is 69%. 11. Yellow light emitted from a sodium lamp has a wavelength of 580 nm. Calculate frequency and wave number of the yellow light? 12. Account for the following: (a) Second ionization enthalpy of Na is higher than Mg. (b) Explain why BeH 2 molecule has zero dipole moment although the Be- H bonds are polar? 13. The successive ionization energies of a certain element are I1 = 589.5 kJ/mol, I2 = 1145 kJ/mol, I3 = 4900 kJ/mol,I4 = 6500 kJ/mol, I5 = 8100 kJ/mol. This pattern of ionization energies suggests that the unknown Element is: a) K b) Si c) Ca d) As. Explain. 14. i) Calculate the wavelength in nm, of visible light having a frequency of 4.37 x 10-14/s. ii) What are frequency and wavelength of a photon emitted during a transition from n = 6 to n = 1 state in the hydrogen atom. 15. Although geometries of NH3 and H2O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss. 16. a)Draw the energy diagram for H2, Be2, N2, O2. b) What is meant by the term bond order. Write the significance of bond order. 17. (a) Define hydrogen bond .Explain its types with suitable examples. (b) Is it weaker or stronger than the van der Waals forces? 18. Explain why the first ionization enthalpy of Carbon is more than that of Boron but the reverse is true for second ionization enthalpy. 19. In each of the following sets, arrange the elements in the increasing order of their negative electron gain enthalpies: (i)C,N,O (ii)O,N,S (iii) Cl,S,Ar (iv)F,Cl,Br 20. The Vividh Bharati station of All India Radio, Delhi, broadcasts on a frequency of 1,368 kHz (kilo hertz). Calculate the wavelength of the electromagnetic radiation emitted by transmitter. Which part of the electromagnetic spectrum does it belong to?

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