5. (a) An insulated copper container of mass 0.250 kg contains 0.350 kg water. B

Question

5. (a) An insulated copper container of mass 0.250 kg contains 0.350 kg water. Both the container and the water are initially at 25.0 0C. Then 0.012 kg of ice at 0.0 0C is added to the container. Eventually the container and contents reach thermal equilibrium at 21.7 0C. (i) What is the total heat released (in J) by the copper container and the 0.350 kg water as they cool down from 25.0 0C to 21.7 0C? (ii) Determine the latent heat of fusion of ice. (b) A glass window has area 5.0 m2 and thickness 2.4 mm. The inside of the window is at 24 oC and the outside is at 11 oC. Calculate the rate of heat loss through the window. (c) A tank of volume 0.400 m3 contains 3.00 x 10-3 kmol of the monatomic gas, He, at 127 ?C. (i) Calculate the mass of one atom of He. (ii) Calculate the root means square speed (vrms) of the He atoms.

Explanation / Answer

(a)

(i) heat released by copper container and water

= 0.25 x 0.39 x (25 - 21.7) + 0.35 x 4.186 x (25-21.7) = 5.16 KJ

(ii) 5.16 KJ = 0.012 x L + 0.012 x 4.186 x 21.7

ie Latent heat of fusion L = 339 KJ/Kg C

Therefore, heat released = 5.16 KJ and latent heat of fusion = 339 KJ/KgC

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