Sample paper 5
Question 1
The boiling point of benzene is 80OC. Estimate its molar heat of vaporization. Assume that it
obeys Trouton's rule.
a) 25.64 kJ mol
-1
b) 31.064 kJ mol
-1
c) 29.96 kJ mol
-1
d) 39.54 kJ mol
-1
e) 40.67 kJ mol
-1
Correct Answer:
b) 31.064 kJ mol
-1
Explanation:
From the Trouton's law ΔH/T
b
= 88 J mol
-1
K
-1
The given data is T
b
= 80
O
C = 80+273 = 353 K
Therefore, ΔH = (88J mol
-1
K
-1
) (353 K) = 31064 J mol
-1
= 31.064 kJ mol
-1
Question 2
The force of attraction between gaseous particles is
a) Strong
b) Weak
c) Very strong
d) Very weak
e) Negligible
Correct Answer:
e) Negligible
Explanation:
Due to very high kinetic energy, gaseous particles easily escape from the attractions of other particles
and tend to maintain very long distances from each other. So, the attraction between gaseous
particles is negligible.
Question 3
The coordination number of hcp structure is
a) 6
b) 4
c) 8
d) 12
e) 2
Correct Answer:
d) 12
Explanation:
Each sphere in hcp structure is in contact with 12 neighbouring spheres. Six spheres are on its own
layer, three on the above layer and remaining three on the below layer. So, the coordination number
of hcp structure is 12. For BCC structure it is 8. For ZnO it is 4.