BCECE Medical BCECE Medical Solved Papers-2009

  • question_answer
    Which of the following will produce the highest rise in temperature?

    A)  67 mL of 1 M NaOH + 33 mL of 0.5 M \[{{H}_{2}}S{{O}_{4}}\]

    B)  33 mL of 1 M NaOH + 67 mL of 0.5 M \[{{H}_{2}}S{{O}_{4}}\]

    C)  40 mL of 1 M NaOH + 60 mL of 0.5 M \[{{H}_{2}}S{{O}_{4}}\]

    D)  50 mL of 1 M NaOH + 50 mL of 0.5 M \[{{H}_{2}}S{{O}_{4}}\]

    Correct Answer: B

    Solution :

    The combination, in which concentration of \[{{H}^{+}}\] is maximum, will produce the highest rise in temperature. [a] Cone. of \[O{{H}^{-}}=\frac{67\times 1-33\times 1}{67+33}\]                 [\[\because \,N=2\,M\] for \[{{H}_{2}}S{{O}_{4}}\]]                 \[=0.34=3.4\times {{10}^{-1}}\]                 \[[{{H}^{+}}]\,[O{{H}^{-}}]=1\times {{10}^{-14}}\] \[\therefore \] \[[{{H}^{+}}]=\frac{1\times {{10}^{-14}}}{3.4\times {{10}^{-1}}}=2.94\times {{10}^{-14}}\] [b]          \[[{{H}^{+}}]=\frac{67\times 1-33\times 1}{67+33}=0.34\] [c]           \[[{{H}^{+}}]=\frac{60\times 1-40\times 1}{60+40}=0.20\] [d] Since concentration and volume of acid and base is equal, the solution is neutral ie,\[[{{H}^{+}}]={{10}^{-7}}\] Hence, mixture given in option [b] will produce the highest rise in temperature.


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