CET Karnataka Medical CET - Karnataka Medical Solved Paper-2011

  • question_answer
    The folllowing data were obtained during the first order decomposition of \[2A(g)\to B(g)+C(s)\]at a constant volume and at a particular temperature
    S. no. Time Total  pressure in Pascal
    1. At the end of 10 min 300
    2. After completion 200
    The rate constant in \[mi{{n}^{-1}}\]is

    A)  \[0.0693\]

    B)  \[69.3\]

    C)  \[6.93\]

    D)  \[6.93\times {{10}^{-4}}\]

    Correct Answer: A

    Solution :

    \[\underset{2-2x}{\mathop{2A(g)}}\,\xrightarrow{{}}\underset{(x)}{\mathop{B(g)}}\,+C(s)\] At the end of reaction, only 1 mole of gas is present whose pressure is 200 Pascal. \[\therefore \] At the beginning of the reaction 2 moles of gas should have a pressure of 400 Pascal. After time 10 min No. of moles present, \[2-2x+x=2-x\] The pressure of 2 moles = 400 \[\therefore \] \[400-x=300\] \[\therefore \] \[x=100\] \[\therefore \] Pressure due to \[2-2x\]moles of A \[=400-200=200\] \[\therefore \] \[k=\frac{2.303}{t}\log \left( \frac{a}{a-x} \right)=\frac{2.303}{10}\log \left( \frac{400}{200} \right)\] \[=\frac{2.303}{10}\log 2=\frac{0.693}{10}\] \[=0.0693{{\min }^{-1}}\]


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