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JAMB Physics 2009 Question 23

Question 23

Change of State and Vapours

A heating coil rated 1000 W is used to boil off completely 2 kg of boiling water. The time required to boil off the water is [specific latent heat of vaporization of water = 2.3 × 106 Jkg−1]

  1. A.1.15 × 104 s.
  2. B.1.15 × 103 s.
  3. C.4.6 × 104 s.
  4. D.4.6 × 103 s.
Show the answer and explanation

Answer: D (4.6 × 103 s.)

Explanation

Heat needed = mL = 2 × 2.3 × 106 = 4.6 × 106 J. Time = 4.6 × 106 ÷ 1000 = 4.6 × 103 s.