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Chemistry XII A, B, C

Ms Rema Devi (PGT Chemistry)

Ms Manju (PGT Chemistry)

Ms Meera (PGT Chemistry)

Date of submission: 23 June 2014

 

CHAPTER :1, “THE SOLID STATE”

QUESTIONS

Q1) An element with molar mass 2.7 x 10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 x 10 3 kg m -3 , what is the nature of the cubic unit cell ?

Q2) How many lattice points are there in one unit cell of each of the following lattice ?

a) Face-centred cubic

b) Face-centred tetragonal

c) Body-centred

Q3) Silver crystallises in fcc lattice. If edge length of the cell is 4.07 x 10 -8 cm and the density is 10.5 g cm -3, calculate the atomic mass of silver ?

Q4) If the radius of the octahedral void is r and radius of the atoms is close packing is R, derive relation between r and R.

Q5) Copper crystallises into a fcc lattice with edge length 3.61 x 10 -8 cm. Show that the calculated density is in agreement with its measured value of 8.92 g cm-3.

Q6 ) Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide , copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor ?

Q7) Gold (atomic radius=0.144nm) crystallises in a face centres unit cell. What is the length of a side of he cell ?

Q8) In terms of band theory , what is the difference:

a) Between a conductor and an insulator

b) Between a conductor and a semiconductor

Q9) Explain the following terms with suitable examples :

a) Schottky defect

b) Frenkel defect

c) Intersititials

d) F-centres

Q10) If NaCl is doped with 10-3 mol % of SrCl2 . What is the concentration of cation vacancies ?

CHAPTER:2 “SOLUTIONS”

Q1) Vapour pressure of chloroform and dichloromethane at 298 K are 200 mm Hg and 415 mm Hg respectively . calculate the vapour pressure of the solution prepared by mixing 25.5g of chloroform and 40 g of dichloromethane at 298 K and also find the mole fraction of each component in vapour phase.

Q2) Define the following terms:

a) Mole fraction

b) Molality

c) Molarity

d) Mass percentage

Q3) Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution . what should be the molarity of such a sample of the acid if the density of the solution is 1.504 g m L-1?

Q4) An antifreeze solution is prepared from 222.6g of ethylene glycol (C2H6O2) and 200g of water. Calculate the molality of the solution. If the density of the solution is 1.072 g mL-1, then what shall be the molarity of the solution ?

Q5) The vapour pressure of the water is 12.3 kPa at 300K. Calculate vapour pressure of 1 molal solution of a non volatile solute in it.

Q6) A solution containing 30g of non-volatile solute exactly in 90g of water has a vapour pressure of 2.8 kPa at 298K, Further , 18 g of water is the added to the solution and the new vapour pressure becomes 2.9 kPa at 298K . calculate

a) Molar mass of the solute

b) Vapour pressure of the water at 298K.

Q7) A 5% solution (by mass) of cane sugar in water has freezing point of 271 K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.

Q8) Two elements A and B form compounds having formula AB2 and AB4. When dissolved in 20 g benzene (C6H6), 1g of AB2 lowers the freezing point by 2.3K whereas 1.0 g ofAB4 lowers it by 1.3 K. The molar depression constant for benzene is 5.1 K kg mol-1. Calculate atomic masses of A and B.

Q9) Suggest the most important type of intermolecular attractive in the following pairs:

a) n-hexane and n-octane

b) I2 and ccl4

c) NaClO4 and water

d) Methanol and acetone

e) Acetonitrile (CH3CN) and Acetone(C3H6O)

Q10) Based on the solute-solvent interactions, arrange the following in order of increasing solubility in n-octane and explain. Cyclohexane, KCL, CH3OH, CH3CN.

Q11) Calculate the mass percentage of aspirin (C9H8O4) in acetonitrile (CH3CN) when 6.5 g of C9H8O4 is dissolved in 450 g of CH3CN.

Q12) Calculate the depression in freezing point of water when 10g of CH3CH2CHCLCOOH is added to 250 g of water .( ka = 1.4 x 10-3, kf =1.86 K kg mol-1)

Q13) Henry’s law constant for the molality of methane in benzene at 298 K is 4.27 x 105 mm Hg. Calculate the solubility of methane in benzene at 298K under 760 mm Hg.

Q14) Determine the amount of CaCl2 (i=2.47) dissolved in 2.5 mg of K2SO4 in 2 litre of water at 25 o C , assuming that it is completely dissociated.


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