JCECE Engineering JCECE Engineering Solved Paper-2005

  • question_answer
    \[1\,\,g\] of steam at \[{{100}^{o}}C\] and equal mass of ice at \[{{0}^{o}}C\] are mixed. The temperature of .the mixture in steady state will be (latent heat of steam\[=540\,\,cal/g\], latent heat of ice \[=80\,\,cal/g)\]:

    A) \[{{50}^{o}}C\]                 

    B) \[{{100}^{o}}C\]

    C) \[{{67}^{o}}C\]                 

    D)  \[{{33}^{o}}C\]

    Correct Answer: B

    Solution :

    Heat taken by ice to raise its temperature to \[{{100}^{o}}C\]is                 \[Q=mL+mc\Delta \theta \] where \[L\] is latent heat, \[c\] is specific heat, and \[\Delta \theta \] is temperature variation. Given,\[m=1\,\,g,\,\,L=80\,\,cal/g\]               \[c=1\,\,cal/g,\,\,\Delta \theta ={{100}^{o}}C\]             \[{{Q}_{1}}=1\times 80+1\times 1\times 100=180\,\,cal\] Heat given by steam when condensed is            \[{{Q}_{2}}={{m}_{2}}{{L}_{2}}=1\times 540=540\,\,cal\] As \[{{Q}_{2}}>{{Q}_{1}}\], hence temperature of mixture will remain\[{{100}^{o}}C\].


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