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JAMB Physics 1997 Question 24

Question 24

Change of State and Vapours

A heating coil rated at 1000 W is used to boil off 0.5 kg of boiling water. The time taken to boil off the water is [Specific latent heat of vaporization of water = 2.3 × 106 J kg−1]

  1. A.1.15 × 109 s
  2. B.1.15 × 107 s
  3. C.1.15 × 105 s
  4. D.1.15 × 103 s
Show the answer and explanation

Answer: D (1.15 × 103 s)

Explanation

Heat needed = mL = 0.5 × 2.3 × 106 = 1.15 × 106 J. Time = 1.15 × 106 ÷ 1000 = 1.15 × 103 s.