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 M_0.98O. 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⁺ =  

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 + CuSO₄ →  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:  

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