Chapter 1&2 test Class XII

Time:  1 hr.                                                                                        Max. Marks: 30

Q1. What is the value of Van’t Hoff factor for: (i) Al₂(SO₄)₃      

(ii) Dimerization of benzoic acid?                                     (1)

Q2. Which magnetic substances can behave as permanent magnets and why?                                                                   (1)

Q3. Which point defect lowers the density of a crystal?                                                                                                                  (1)

Q4. Which colligative property is preferred for the calculation of molecular mass of macromolecules?                     (1)

Q5. Which type of semi-conductor is formed when: (i) Si is doped with P, (ii) Si is doped with In.                                                (1)

Q6. Calculate the fraction of M²⁺ and M³⁺ ions present in M_0.98O_1.00 .                                                                                        (2)

Q7. Determine amount of CaCl₂ dissolved in 2.5 L of water such that its osmotic pressure is 0.75 atm at 27⁰C, assuming that it is completely dissociated.                                                                                                                                         (2)

Q8. Why LiCl acquires pink colour when heated in Li vapours?                                                                                                     (2)

Q9. (i) Atoms of element B form hcp lattice and those of the element A occupy 2/3 rd of tetrahedral voids. What is the formula of the compound formed by the elements A and B?                                                                                                      (2)

(ii) State the condition resulting in reverse osmosis.

Q10. Gold (atomic mass = 197 u, atomic radius = 0.144nm) crystallises in fcc lattice. Determine the density of the gold.                                                                                                                               (2)

Q11. Determine the molarity of an antifreeze solution containing 250g water mixed with 222g ethylene glycol (C₂H₆O₂). The density of this solution is 1.07g/mL.                                                                                                                         (2)

Q12. Derive the relationship between relative lowering of vapour pressure and molecular mass of solute.            (2)

Q13. Vapour pressure of chloroform (CHCl₃ ) and dichloromethane (CH₂Cl₂) at 298 K are 200 mm Hg and 415 mm Hg respectively.(i) Calculate the vapour pressure of the solution prepared by mixing 25.5 g of CHCl₃ and 40 g of CH₂Cl₂ at 298 K and,(ii) mole fraction of each component in vapour phase.                                                                                                          (3)

Q14. Write main difference between the following with an example of each:                        

(i) Ideal and Non-ideal solution

(ii) Schottky and Frenkel Defect.                                                                                                                     (3)

Q15. a) Draw the graph showing depression of the freezing point of a solvent in a solution. Also, define Cryoscopic constant.

b) Two elements A and B form compounds having formula AB₂ and AB₄. When dissolved in 20g of benzene, 1g of  AB₂ lowers the freezing point by 2.3K whereas 1g of AB₄ lowers the freezing point by 1.3K. The molal depression constant for benzene is 5.1 KKg/mol. Calculate atomic messes of A and B.                                                                                                      (5)