IS
17. How much heat is required to raise the temperature of 20 g of mercury from 20 °C to 30 °C?
[Cmercury = 140 J kg 'K')
Answers
Answer:
6863.6 joules
Explanation:
1
in order to change 20 g of mercury at 20 degree Celsius to mercury vapour at boiling point
heat energy is needed to increase the temperature of the mercury to its boiling point and then to change the state of the mercury from liquid to vapour
2
heat energy needed to increase the temperature of the mercury to its boiling point
q= m x c x t
m= 20 g = .02 kg
c= specific heat
=140 j/(kg k)
t = temperature change
= 357 - 20
= 337
q= .02 x 140 x 337
=943.6 joules
3
heat energy needed to change the state of the mercury from liquid to vapour
q= m x l
l= latent heat of vaporization = 2.96 x 10 ^ 5
m= .02 kg
q= .02 x 2.96 x 10 ^ 5
= 5920 joules
total heat energy neede is 943.6+5920 =6863.6 joules
Given:
Difference in temperature = 20°C to 30°C
Mass of mercury = 20 g
Specific heat of mercury = 140 J/kg K
Solution:
Since the heat required is:
Q = mcΔT
= 0.02 * 140 * (30-20)
= 28 J
Therefore, the amount of heat required to raise the temperature of 20 g of mercury from 20 °C to 30 °C is 28 J.