JEE Main & Advanced JEE Main Paper (Held On 15 April 2018) Slot-II

  • question_answer
    Given
    (i) \[2F{{e}_{2}}{{O}_{3}}(s)\to 4Fe(s)+3{{O}_{2}}(g);\] \[{{\Delta }_{r}}{{G}^{o}}=+1487.0kJmo{{l}^{-1}}\]
    (ii) \[2CO(g)+{{O}_{2}}(g)\to 2C{{O}_{2}}(g);\] \[{{\Delta }_{r}}G{}^\circ =-514.4kJmo{{l}^{-1}}\]
    Free energy change, \[{{\Delta }_{r}}G{}^\circ \] \[2F{{e}_{2}}{{O}_{3}}(s)+6CO(g)\to 4Fe(s)+6C{{O}_{2}}(g)\] will be.                       [JEE Online 15-04-2018 (II)]

    A) \[-112.4kJ\,\,mo{{l}^{-1}}\]        

    B) \[-56.2\text{ kJ mo}{{\text{l}}^{-1}}\]    

    C) \[-208.0\text{ kJ mo}{{\text{l}}^{-1}}\]  

    D) \[-168.2\text{ kJ mo}{{\text{l}}^{-1}}\]

    Correct Answer: B

    Solution :

    (i) \[2F{{e}_{2}}{{O}_{3}}(s)\to 4Fe(s)+3{{O}_{2}}(g);\] \[{{\Delta }_{r}}{{G}^{o}}=+1487.0kJmo{{l}^{-1}}\] (ii) \[2CO(g)+{{O}_{2}}(g)\to 2C{{O}_{2}}(g);\] \[{{\Delta }_{r}}{{G}^{o}}=-514.4kJ\,\,mo{{l}^{-1}}\] Multiply above reaction with 3 (iii) \[6CO(g)+3{{O}_{2}}(g)\to 6C{{O}_{2}}(g);\] \[{{\Delta }_{r}}{{G}^{o}}=3\times -514.3=-1543.2kJ\,\,mo{{l}^{-1}}\] When we add reaction (i) and reaction (iii), we get reaction (iv) (iv) \[2F{{e}_{2}}{{O}_{3}}(s)+6CO(g)\to 4Fe(s)+6C{{O}_{2}}(g)\] Free energy change, \[{{\Delta }_{r}}{{G}^{o}}\] for the reaction will be. \[1487.0-1543.2=-56.2kJmo{{l}^{-1}}\]


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