JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law, with\[{{t}_{1/2}}=3.00\,\,h\].What fraction of sample of sucrose remains after\[8\,\,h\]?

    A) \[1.023\,\,M\]                  

    B) \[0.8725\,\,M\]

    C) \[0.023\,\,M\]                  

    D) \[0.1576\,\,M\]

    Correct Answer: D

    Solution :

    For first order reactions,                 \[k=\frac{0.693}{{{t}_{1/2}}}=\frac{0.693}{(3.0)}\]                 \[t=\frac{2.303}{K}\log \frac{[{{A}_{0}}]}{[A]}\] Thus,\[\log \frac{[{{A}_{0}}]}{[A]}=\frac{kxt}{2.303}=\frac{0.693}{3}\times \frac{8}{2.303}=0.804\]                 \[\frac{{{[A]}_{0}}}{[A]}=\text{Antilog}\,\,0.8024=6.345\]                 \[{{[A]}_{0}}=1\,\,M;\]                 \[[A]=\frac{1}{6.345}=0.1576\,\,M\]


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