(i) Heat of sublimation of \[Mg(s)=+147.7\,\,kJ\,\,mo{{l}^{-1}}\] |
(ii) lionisation energy of\[Mg(g)\]to form \[M{{g}^{2+}}(g)=2189.0\,\,kJ\,\,mo{{l}^{-1}}\] |
(iii) Bond dissociation energy for \[{{O}_{2}}=498.4\,\,kJ\,\,mo{{l}^{-1}}\] |
(iv) First electron affinity of \[O(g)=-141.0\,\,kJ\,\,mo{{l}^{-1}}\] |
(v) Heat formation of \[MgO=-601.7\,\,kJ\,\,mol-1\] |
(vi) Lattice energy of \[MgO=-3791.0\,\,kJ\,\,mo{{l}^{-1}}\] |
A) \[235.6\,\,kJ\,\,mo{{l}^{-1}}\]
B) \[468.7\,\,kJ\,\,mo{{l}^{-1}}\]
C) \[544.4\,\,kJ\,\,mo{{l}^{-1}}\]
D) \[744.4\,\,kJ\,\,mo{{l}^{-1}}\]
Correct Answer: D
Solution :
Stepwise formation of \[MgO\] involvesStep | Reaction | \[\Delta H\]in\[KJ\,\,mo{{l}^{-1}}\] |
(i) | \[Mg(s)\to Mg(g)\] | \[147.7\] |
(ii) | \[Mg(g)\to M{{g}^{2+}}+2{{e}^{-}}\] | \[2189.0\] |
(iii) | \[\frac{1}{2}{{O}_{2}}(g)\to O(g)\] | \[498.4/2\] |
(iv) | \[O(g)+1{{e}^{-}}\to {{O}^{-}}(g)\] | \[-141.0\] |
(v) | \[{{O}^{-}}(g)t{{e}^{-}}\to {{O}^{2-}}(g)\] | \[q\] |
(vi) | \[M{{g}^{2+}}(g)+{{O}^{2-}}(g)\to MgO(s)\] | \[-3791.0\] |
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