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NEET Chemistry Thermodynamics / रासायनिक उष्मागतिकी NEET PYQ-Thermodynamics

  • question_answer
    Change in enthalpy for reaction \[2{{H}_{2}}{{O}_{2}}(l)\xrightarrow{{}}2{{H}_{2}}O(l)+{{O}_{2}}(g)\] If heat of formation of \[{{H}_{2}}{{O}_{2}}(l)\] and \[{{H}_{2}}O(l)\] are \[-188\] and \[-286\text{ }kJ/mol\] respectively:       [AIPMT 2001]

    A)  \[-196\text{ }k\text{ }J/mol\]

    B)       \[+\text{ }196\text{ }k\text{ }J/mol\]

    C)  \[+948\text{ }k\text{ }J/mol\]

    D)       \[-948\text{ }k\text{ }J/mol\]

    Correct Answer: A

    Solution :

    \[2{{H}_{2}}{{O}_{2}}(l)\xrightarrow{{}}2{{H}_{2}}{{O}_{2}}(l)+{{O}_{2}}(g)\Delta H=?\]
                \[\Delta H=[2\times \Delta {{H}_{f}}\,\text{of}\,{{H}_{2}}O(l)+(\Delta {{H}_{f}}\,\text{of}\,{{O}_{2}})]\]
                            \[-(2\times \Delta {{H}_{f}}\,\text{of}\,{{H}_{2}}{{O}_{2}}(l))]\]
                            \[=[(2\times -286)+(0)-(2\times -188)]\]
                            \[=[-572+376]\]
                            \[=-196\,\,kJ\,/mol\]


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