KVPY Sample Paper KVPY Stream-SX Model Paper-10

  • question_answer
    The following reaction is performed at 298 K.\[2NO\left( g \right)+{{O}_{2}}(g)2N{{O}_{2}}\left( g \right)\] The standard free energy of formation of \[\operatorname{NO}\left( g \right)\]is\[86.6 kJ/mol at 298 K\]. What is the standard free energy of formation of \[\operatorname{NO}\left( g \right) at 298 K?\] \[\left( {{K}_{P}} = 1.6 \times 1{{0}^{12}} \right)\]

    A) \[86600-\frac{in\left( 1.6\times 1{{0}^{12}} \right)}{R\left( 298 \right)}\]

    B) \[0.5\left[ 2\times 86,600-R\left( 298 \right)In\left( 1.6\times 1{{0}^{12}} \right) \right]\]

    C) \[\operatorname{R}\left( 298 \right)in\left( 1.6\times 1{{0}^{12}} \right)-86600\]

    D) \[86600+R\left( 298 \right)in\left( 1.6\times 1{{0}^{12}} \right)\]

    Correct Answer: B

    Solution :

    \[\Delta \operatorname{G}_{NO\left( g \right)}^{{}^\circ }=86.6\operatorname{KJ}/\operatorname{mol}=86600\operatorname{J}/mol\]
          \[\operatorname{G}_{N{{O}_{2}}(g)}^{{}^\circ }=xJ/mol\]
          \[\operatorname{T}=298,{{K}_{P}}=1.6\times 1{{0}^{12}}\]
           \[\Delta \operatorname{G}{}^\circ =-RT\,ln\,{{K}_{\operatorname{P}}}\]   
    Give equation, \[2NO\left( g \right)+{{O}_{2}}\left( g \right)2{{\operatorname{NO}}_{2}}\left( g \right)\]\[\therefore \,2\Delta \operatorname{G}_{N{{O}_{2}}}^{{}^\circ }-2\Delta \operatorname{G}_{NO}^{{}^\circ }=-\operatorname{R}\left( 298 \right)\ln \left( 1.6\times {{10}^{12}} \right)\]\[2\Delta G_{N{{O}_{2}}}^{{}^\circ }-2\times 86600\] 
                            \[=-R\left( 298 \right)\ln \,\left( 1.6\times {{10}^{12}} \right)\] 
    \[2\Delta G_{N{{O}_{2}}}^{{}^\circ }=2\times 86600-\operatorname{R}\left( 298 \right)\ln \left( 1.6\times {{10}^{12}} \right)\]    \[\begin{align}   & \Delta G_{N{{O}_{2}}}^{{}^\circ }=\frac{1}{2}[2\times 86600-R\left( 298 \right) \\  & \ln \,\left( 1.6\times {{10}^{12}} \right)] \\ \end{align}\]
    \[=0.5[2\times 86600-R\left( 298 \right)\ln \,\left( 1.6\times {{10}^{12}} \right)\]


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