Class 12th

69.  (i) - (d); (ii)- (a); (iii)- (b); (iv)- (e); (v)- (f)

68.  (i) - (c); (ii)- (a); (iii)- (e); (iv)- (b)

67.  (i) - (c); (ii)- (a); (iii)- (b)

66.  (i) - (b); (ii)- (a); (iii)- (d); (iv)- (e); (v)- (c)

65.  (i) - (c); (ii)- (d); (iii)- (b); (iv)- (e); (v)- (a)

64. Osmium has the capacity to expands its octet by utilising all the electrons from its 6s and 5d orbitals this results it to attain an oxidation state of +8.

Both the statements assertion and reason are correct but reason is not the correct explanation of assertion. The correct option is B.

63. Cu lies below hydrogen in electrochemical series and has positive electrode potential. hence cannot liberate hydrogen from acids. 

Both the statements assertion and reason are correct and reason is the correct explanation of assertion. 

62. Actinoids are more reactive than lanthanoids as they involve their 5d-orbital in the bond formation process while due to effectively shielded and greater nuclear charge 4f-orbitals are not available for bonding. Thus, lanthanoids comparatively form less complexes than actinoids. 

Assertion is not true but reason is true.