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JEE Main201910 Jan 2019Evening ShiftPhysicsKinetic Theory of GasesActual

An unknown metal of mass 192   g heated to a temperature of 100 ° C was immersed into a brass calorimeter of mass 128 g containing 240   g of water at a temperature of 8.4 o C . Calculate the specific heat of the unknown metal if water temperature stabilizes at 21.5 o C . ( Specific heat of brass is 394 J   k g - 1 K - 1 )

Options

  1. A916 J k g - 1 K - 1
  2. B458 J k g - 1 K - 1
  3. C654 J k g - 1 K - 1
  4. D1232 J k g - 1 K - 1

Correct answer

A. 916 J k g - 1 K - 1

Step-by-step solution

Conservation of energy: m s Δ T = m b s b + m w s w Δ T w 192 × 10 - 3 s 100 - 21.5 = 128 × 394 + 240 × 4182 × 10 - 3 × 21.5 - 8.4 s = 50432 + 1003680 13.1 15072 = 916 . 19 ≃ 916 J   k g - 1   K - 1

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