JEE Main & Advanced JEE Main Paper (Held On 19 May 2012)

  • question_answer
    When \[C{{O}_{2(g)}}\]is passed over red hot coke it partially gets reduced to \[CO(g).\]Upon passing L of \[C{{O}_{2}}(g)\] over red hot coke, the total volume of the gases increased to 700 mL. The composition of the gaseous mixture at STP is     JEE Main  Online Paper (Held On 19  May  2012)

    A) \[C{{O}_{2}}=300mL;CO=400mL\]

    B)                        \[C{{O}_{2}}=0.0mL;CO=700mL\]

    C)                        \[C{{O}_{2}}=200mL;CO=500mL\]

    D)                        \[C{{O}_{2}}=350mL;CO=350mL\]

    Correct Answer: A

    Solution :

                     \[C{{O}_{2}}+C\xrightarrow[{}]{{}}2CO\] Stoichoimetry ratio is 1 : 2 AT STP, P=1 atm, T=273 K, R = 0.0821 Initial moles of \[C{{O}_{2;}}n(C{{O}_{2}}\text{initial})=\frac{PV}{RT}\] \[=\frac{1\times 0.5}{0.0821\times 273}=0.022\,\text{mole}\] In final mixture no. of moles; \[n(C{{O}_{2}}/CO\,\text{mixture)}\] \[=\frac{1\times 0.7}{0.0821\times 273}=0.031\] Increase in volume is by = 0.031 - 0.022 = 0.009 mole of gas Final no. of moles of CO i.e. \[{{n}_{(CO\,final)}}\] \[{{n}_{(CO\,final)}}=2{{n}_{(C{{O}_{2}}\,initial)}}-{{n}_{(C{{O}_{2}}final)}}\] \[=2(0.022)-{{n}_{(C{{O}_{2}}final)}}\]                                    ?(i) \[{{n}_{(CO\,final)}}=0.044-2{{n}_{(C{{O}_{2}}final)}}\]                  ?(ii) \[\therefore \]Now,\[{{n}_{(COfinal)}}+{{n}_{(COfinal)}}=0.031\] \[{{n}_{(C{{O}_{2}}final)}}=0.031-{{n}_{(CO\,final)}}\] Substituting (ii) in eq. (i) \[{{n}_{(CO\,final)}}=0.044-[0.031{{-}_{n(CO\,final)]}}\] \[{{n}_{(CO\,final)}}=0.044-0.062+2{{n}_{(CO\,final)}}\] \[{{n}_{(CO\,final)}}=0.018mol.\] Volume of \[CO=V=\frac{nRT}{P}=\frac{0.018\times 0.0821\times 273}{1}\] \[=0.40\]Litre and volume of \[C{{O}_{2}}=0.7\]litre ? 0.4 litre  = 0.3 litre \[\therefore \]\[C{{O}_{2}}=300mL\,CO=400mL\]


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