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JEE Main & Advanced JEE Main Paper (Held On 10-Jan-2019 Evening)

  • question_answer
    An unknown metal of mass 192 g heated to a temperature of \[100{}^\circ C\] was immersed into a brass calorimeter of mass 128 g containing 240 g of water at a temperature of \[8.4{}^\circ \,C\]. Calculate the specific heat of the unknown metal if water temperature stabilizes at \[21.5{}^\circ C\]. (Specific heat of brass is \[394\text{ }J\text{ }k{{g}^{-1}}{{K}^{-1}}\]) [JEE Main Online Paper (Held On 10-Jan-2019 Evening]

    A) 458 J \[394\text{ }J\text{ }k{{g}^{-1}}{{K}^{-1}}\]                

    B) 1232 J \[394\text{ }J\text{ }k{{g}^{-1}}{{K}^{-1}}\]

    C) 654 J \[394\text{ }J\text{ }k{{g}^{-1}}{{K}^{-1}}\]

    D)                  916 J \[394\text{ }J\text{ }k{{g}^{-1}}{{K}^{-1}}\]

    Correct Answer: D

    Solution :

    Final temperature \[=\text{ }21.5{}^\circ C\] Total heat gain = 0 \[192\times 5\left( 21.5-100 \right)+\frac{128}{1000}\times 394\left( 21.5-8.4 \right)\] \[+\text{ }240\times 4.2\text{ }\left( 21.5-8.4 \right)=0\] \[-\,5\times 15072+13865.45=0\] \[S=916\text{ }J\text{ }k{{g}^{-1}}\,{{K}^{-1}}\]


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