NEET AIPMT SOLVED PAPER 1999

  • question_answer
                    If 1 g of steam is mixed with 1 g of ice, then the resultant temperature of the mixture is:              

    A)                 \[{{270}^{\text{o}}}C\]

    B)                            \[{{230}^{\text{o}}}C\]

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

    D)                                            \[{{50}^{\text{o}}}C\]

    Correct Answer: C

    Solution :

                    Heat required by 1 g ice at \[{{0}^{\text{o}}}C\] to melt into 1 g water at \[{{0}^{\text{o}}}C\],                 Q1 = mL                (L = latent heat of fusion)                 \[=1\times 80\,\,=80\,cal\]                          (L = 80 cal/g )                 Heat required by 1 g of water at \[{{0}^{\text{o}}}C\] to boil at \[{{100}^{\text{o}}}C\],                 \[{{Q}_{2}}=mc\Delta \theta \]                  (c = specific heat of water)                 \[=1\times 1\,\,(100-0)\]                (c = 1 cal/g °C)                 = 100 cal                 Thus, total heat required by 1 g of ice to reach a temperature of \[{{100}^{\text{o}}}C\],                 \[Q={{Q}_{1}}+{{Q}_{2}}\]                 \[=80+100=180\,cal\]                 Heat available with 1g of steam to condense into 1 g of water at \[{{100}^{\text{o}}}C\],                 \[Q'=mL'\]                          (L' = latent heat of vaporisation)                 \[=1\times 536\,cal\]                    (L? = 536 cal/g)                 = 536 cal                 Obviously, the whole steam will not be condensed and ice will attain temperature of \[{{100}^{\text{o}}}C\]. Thus, the mixture of temperature is \[{{100}^{\text{o}}}C\].


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