JEE Main & Advanced Sample Paper JEE Main Sample Paper-44

  • question_answer
    For the reaction,\[2A(g)+B(g)\,\,C(g)+D(g);\]\[{{K}_{c}}={{10}^{12}}\]. If the initial moles of A, B, C and D are 2, 1,7 and 3 moles respectively in 1 L vessel, what is the equilibrium concentration of A ?

    A)  \[4\times {{10}^{-4}}\]                  

    B)  \[2\times {{10}^{-4}}\]

    C)  \[{{10}^{-4}}\]                               

    D)  \[8\times {{10}^{-4}}\]

    Correct Answer: A

    Solution :

     \[2A(g)\,\,+\,\,B(g)\,\,\,\,C(g)\,\,+\,\,D(g)\] Initial moles    1                       1              7      3 At equi.           \[2-2x\]      \[1-x\]      \[7+x\]   \[3+x\] \[\therefore \] Due to very high value of K, we can assume that reactant almost gets converted into products, so \[1-x=y\] \[2-2x=2y\,\,\Rightarrow \,\,x\sim 1\] \[\therefore \]    \[{{10}^{12}}=\frac{[C]\,[D]}{{{[A]}^{2}}\,[B]}\] \[{{10}^{12}}=\frac{8\times 4}{{{(2y)}^{2}}(y)}\] \[{{y}^{3}}=8\times !{{0}^{-12}}\] \[\Rightarrow \]            \[y=2\times {{10}^{-4}}\] \[\therefore \] Equilibrium concentration of \[A=2y\] \[=2\times 2\times {{10}^{-4}}=4\times {{10}^{-4}}\]


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