WAEC Physics 2020 Objective — Question 35
Question 35 of 50 from the West African Examinations Council (WAEC) Physics 2020 Objective paper, with the correct answer and a full explanation.
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The sketched graph above illustrates the heating curve of a 0.02 kg of water. Estimate the specific latent heat of vapourization of water.
- A. 2.25x10^6 J/kgCorrect
- B. 4.17x10^3 J/kg
- C. 2.00x10^3 J/kg
- D. 1.00x10^3 J/kg
Explanation
From the given graph, the temperature remained constant from 8x10^3 J till 53x10^3 J, indicating the latent heat. Thus, q=(53x10^3)-(8x10^3)=45x10^3 J. Using q=ml, where l=latent heat of vapourization: l=(45x10^3)/0.02=2.25x10^6 J/kg.
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