(a) What is meant by specific latent heat of fusion of a substance? (b) In an experiment to determine the specific latent heat of vaporization...

      

(a) What is meant by specific latent heat of fusion of a substance?
(b) In an experiment to determine the specific latent heat of vaporization of water, steam at 100ºC was passed into water
contained in a well-lagged copper calorimeter. The following measurements were made:
? Mass of calorimeter = 60g
? mass of water + calorimeter = 145g
? Final mass of calorimeter + water + condensed steam = 156g
? Final temperature of the mixture = 48oC
[Specific heat capacity of water = 4200JKg¯¹k¯¹ and specific heat capacity of copper = 390JKg¯¹k¯¹]
Determine the;
(i) mass of condensed steam.
(ii) The heat gained by the water and calorimeter if the initial temperature of the calorimeter and water is 20ºC.
(iii) Given that Lvis the specific latent heat of vaporization of steam, write an expression for the heat given out by steam.
(iv) Determine the value of Lv above (2marks)
(v) State the assumption made in the above experiment

  

Answers


john
(a) What is meant by specific latent heat of fusion of a substance? (1mark)
The amount of heat energy required to change a unit mass of solid to liquid at constant temperature.
(b) (i) mass of condensed steam. (1mk)
Mass of steam = 156 - 145 = 11 g
(ii) Heat gained by water + heat gained by calorimeter = 0.085 x 4200 (48-20) + 0.06 X 390(48-20)
= 10,651.2 J
(iii) Heat lost by steam=Heat lost by condensing steam + heat lost by condensed steam
= 0.011 X Lv+ 0.011 X 4200 X (100 – 48)
= 0.011Lv+ 2,402.4
(iv) Heat lost by steam+heat lost by condensed water = heat gained by water + heat gained by calorimeter
0.011 XLv+ 0.011 X 4200 X (100 – 48) = 0.085 X 4200 (48-20) + 0.06 X 390(48-20)
Lv= 749,890.9091JKg-1
(v) There are no heat losses
There is no change in mass
john3 answered the question on November 2, 2017 at 21:06


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