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NEET Chemistry Thermodynamics / रासायनिक उष्मागतिकी Question Bank Self Evaluation Test - Thermodynamics

  • question_answer
    The molar heat capacity \[\left( {{C}_{p}} \right)\] of \[C{{D}_{2}}O\] is 10 cals at 1000 K. The change in entropy associated with cooling of 32 g of \[C{{D}_{2}}O\] vapour from 1000 K to 100 K at constant pressure will be: (D = deuterium, atomic mass = 2 u)

    A) \[23.03\text{ }cal\text{ }de{{g}^{-1}}\]  

    B) \[-23.03\text{ }cal\text{ }de{{g}^{-1}}\]

    C) \[2.303\text{ }cal\text{ }de{{g}^{-1}}\]            

    D) \[-2.303\text{ }cal\text{ }de{{g}^{-1}}\]

    Correct Answer: B

    Solution :

    [b] Given, \[{{C}_{P}}=10\] cals at 1000 K \[{{T}_{1}}=1000K.\,{{T}_{2}}=100K\] \[m=32\,g\] \[\Delta S=?\] at constant pressure \[\Delta S={{C}_{p}}\] In \[\frac{{{T}_{2}}}{{{T}_{1}}}\] \[=2.303\times {{C}_{p}}log\frac{{{T}_{2}}}{{{T}_{1}}}\] \[=2.303\times 10log\frac{100}{1000}\] \[=-23.03\text{ }cal\text{ }de{{g}^{-1}}\]


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