JEE Main & Advanced Physics Thermometry, Calorimetry & Thermal Expansion Question Bank Critical Thinking

  • question_answer
    The temperature of equal masses of three different liquids A, B and C are 12ºC, 19ºC and 28ºC respectively. The temperature when A and B are mixed is 16ºC and when B and C are mixed is  23ºC. The temperature when A  and C are mixed is                                                              [Kerala PET 2005]

    A)            18.2ºC                                     

    B)            22ºC

    C)            20.2ºC                                     

    D)            25.2ºC

    Correct Answer: C

    Solution :

                       Heat gain = heat lost CA(16 ?12) = CB (19 ? 16) Þ \[\frac{{{C}_{A}}}{{{C}_{B}}}\] = \[\frac{3}{4}\] and CB(23 ? 19) = CC (28 ? 23) Þ\[\frac{{{C}_{B}}}{{{C}_{C}}}\] = \[\frac{5}{4}\] Þ \[\frac{{{C}_{A}}}{{{C}_{C}}}=\frac{15}{16}\]                                                            ...(i) If q is the temperature when A and C are mixed then, \[{{C}_{A}}(\theta -12)\] = \[{{C}_{C}}(28-\theta )\] Þ \[\frac{{{C}_{A}}}{{{C}_{C}}}\]\[=\frac{28-\theta }{\theta -12}\]  ...(ii) On solving equation (i) and (ii) q = 20.2ºC.


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