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JAMB Physics 1985 Question 19

Question 19

Quantity of Heat

Two liquids, P at a temperature of 20°C and Q at a temperature of 80°C have specific heat capacities of 1.0 J kg−1 °C−1 and 1.5 J kg−1 °C−1 respectively. If equal masses of P and Q are mixed in a lagged calorimeter, then the equilibrium temperature is

  1. A.44°C
  2. B.50°C
  3. C.56°C
  4. D.60°C
  5. E.70°C.
Show the answer and explanation

Answer: C (56°C)

Explanation

Heat lost by Q = heat gained by P: 1.5(80 − θ) = 1.0(θ − 20), so 120 − 1.5θ = θ − 20 and θ = 56°C.