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PHYSICAL CHEMISTRY, P-BLOCK ELEMENTS, METALLURGY

1. In the mineral spinel MgAl2O4 oxide ions formed ccp lattice Mg+2 ions occupy tetrahedral voids while Al+3 ions occupy the octahedral voids then percentage of tetrahedral, octahedral voids occupied by Mg+2 and Al+3 ions respectively
Ans: 12.5, 50

Solution:
 

 

2. LiCl has rock salt structure, with an edge length of 6.0 Aº. If anions are in contact, the ionic radius of chloride ion is
Ans: 2.12 Aº 
Solution:
 

 

 3. How many unit cells are present in cube shaped ideal crystal of NaCl of mass 1.00 g?
Ans: 2.57 × 1021 unit cells
Solution:
1 mole unit cell _______ 4 mole NaCl
 6 × 1023 unit cell present in 4 × 58.5g Nacl ? _______ 1g

4. Experimentally it was found that a metal oxide has formula M0.98O. Metal M, present as M2+ and M3+ in its oxide. Fraction of the metal which exists as M3+ would be
Ans: 4.08 %
Solution:
Number of M3+ ions = x
Number of M2+ ions = 98-x
x = 4
M3+ =   × 100 = 4.08%

 

5. Calculate the mass of a non-volatile solute (molar mass 40 gmol−1) which should be dissolved in 114g Octane to reduce its vapour pressure to 80%
Ans: 8g
Solution:

6. A 5% solution of cane sugar (mol.wt.=342) is isotonic with 1% solution of substance X. The molecular weight of X is
Ans: 68.4
Solution:

7. The mole fraction of C6H6 in a solution containing 37.5 g of camphor in 39.0 of benzene was 0.667. The molecular weight of camphor is found to be
Ans: 150.2
Solution:


 

8. A 0.2 molal solution of KCl freezes at 0.68ºC. If Kf for H2O is 1.86, the degree of dissociation of KCl is
Ans: 83%
Solution:
ΔT = i × Kf × m = 0.68 = i × 1.86 × 0.2
i =1.83

Ionization = 83%
 

9. The position of some metals in the electro chemical series in decreasing electro positive character is given Mg > Al > Zn > Cu > Ag . What will happen if a copper spoon is used to stir a solution of aluminium nitrate?
Ans: There is no reaction
Solution:
Copper can’t displace Al from Al(NO3)3 because of low SRP value

 

10. Zinc reacts with CuSO4 according to the equation Zn + CuSO  ZnSO4 + Cu If excess of Zinc is added to 100.0 ml of 0.05 M CuSO4, the amount of copper formed in moles will be
Ans: 0.005
Solution: 

 

11. The E0 at 25ºC for the following reaction at the indicated concentrations is 1.50 V. Calculate the ΔG in kJ at 25ºC
 
Ans: -422.83
Solution:

 

12. The specific conductance and equivalent conductance of a saturated solution of BaSO4 are 8 × 10−5 ohm−1 cm−1 and 8000 ohm−1cm2equi−1 respectively. Hence sp K of BaSO4 is
Ans: 2.5 × 10−11M2
Solution: 

 

13. The rate of a reaction can be increased in general by all the factors except
Ans: increasing the activation energy
Solution:
Conceptual

 

14. From the following data for the decomposition of N2O5 at 30ºC , find out the rate constant ( in min−1). Volume of O2 after 10 mins of the reaction = 90 ml. Volume of O2 after completion of the reaction = 100ml
Ans: 0.2303
Solution:

15. A first order reaction was commenced with 0.2 M solution of the reactants. If the molarity of the solution falls to 0.02 M after 100 minutes the rate constant of the reaction is
Ans: 2.3 × 10−2 min−1
Solution:

16. The half-life period of a first order reaction is 15 minutes. The amount of substance left after one hour will be:
Ans: 1/16 of the original amount
Solution:

Amount of remaining after 60 min = 
 

17. The auto catalyst in the decomposition of arsine to Arsenic and H2 is
Ans: As
Solution:
Conceptual

 

18. The gold numbers of protective colloids (I) gelatin, (II) albumin, and (III) potato starch are 0.005 – 0.001, 0.1-0.2 and 25 respectively. The correct order of efficiency of protective action of the colloid is:
Ans: I > II > III
Solution:
Weight in milligrams of a protective colloid which checks the coagulation of 10 ml of a given gold solution on adding 1 ml of a 10% solution of sodium chloride is called gold number

 

19. Cow milk is an example of natural emulsion stabilized by
Ans: caesin
Solution:
Conceptual

 

20. The minimum mass of potato starch required to be added to 10 mL of gold sol to just prevent its coagulation by adding 1 mL of 10% NaCl solution is
Ans: 25 mg
Solution:
Conceptual

 

21. Silver is displaced when zinc is added to aqueous sodium argento cyanide. This method of extracting silver is an example for
Ans: Hydro metallurgy
Solution:

 

22. In the purification of Al by Hoope’s process the correct statement is
1) electrolytic cell is iron cell and it contains three layer mass
2) upper layer is pure Al and Carbon rods in it are cathode and the bottom layer contains impure Al and carbon lining of the cell is anode
3) Electrolyte is the middle layer with fused mixture of flourides Na, Al, Ba
4) All the above
Ans: 4 (All the above)
Solution:
Conceptual

 

23. A metal X on heating in nitrogen gas gives Y, Y on treatment with H2O gives a colourless gas which when passed through CuSO4, solution gives a blue colour, Y is
Ans: Mg3N2
Solution:
Conceptual

 

24. The percentage of p-character in the orbitals forming p-p bonds in P4 is
Ans: 33
Solution:
Conceptual

 

25. A chalcogen combines directly with hydrogen with great difficulty to form a hydride. This chalcogen also burn in air to form a solid polymeric dioxide and has got the highest electrical resistance amongst metals. The chalcogen is
Ans: Te
Solution:
Conjugate base of strong acid acts as a weak base
HClO4  + 1 + x −8 = 0;  x = +7

 

26. Oxygen does not form OF6 because
Ans: there are no vacant d-orbitals available
Solution:
H-bonds are not present in HI

 

27.  
Ans:  
Solution:
XeF6 + 3H2O  XeO3 + 6HF

28. Hydrogen bonding does not play any role in boiling point of
Ans: HI
Solution:
Conceptual

 

29.  
Which of the following statement is true, regarding "X"
     i) It is pyramidal shape                    ii) Central atom undergoes sp2 hybridisation
     iii) It contains 3σ and 3π bonds      iv) Central atom O. N is +6
Ans: i, iii & iv are correct
Solution:

 

30. The structure of XeOF4 is
Ans: Square pyramidal
Solution:
Conceptual

Posted Date : 19-02-2021

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