NEET Sample Paper NEET Sample Test Paper-27

  • question_answer The enthalpies of formation of \[{{C}_{2}}{{H}_{2(g)}}\] and \[{{C}_{6}}{{H}_{6(g)}}\]at 298 K are 230 and \[85\text{ }kJ\text{ }mo{{l}^{-1}}\]respectively. The enthalpy change \[\Delta H\] for the polymerisation of acetylene at 298 K is

    A)  \[+205\text{ }kJ\text{ }mo{{l}^{-1}}\]                 

    B)  \[-205\text{ }kJ\text{ }mo{{l}^{-1}}\]

    C)  \[+605\text{ }kJ\text{ }mo{{l}^{-1}}\]    

    D)  \[-605\text{ }kJ\text{ }mo{{l}^{-1}}\]

    Correct Answer: D

    Solution :

    \[3{{C}_{2}}{{H}_{2}}\xrightarrow{Polymerisation}{{C}_{6}}{{H}_{6}}\]   \[\Delta H\] = enthalpy of product - enthalpy of reactant \[=85-3(230)\] \[=85-690\] \[=-605\,kJ\,mo{{l}^{-1}}\]

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