- #1
Peter G.
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Hi
The mass of liquid nitrogen in an open beaker is found to have decreased by 46.3 g in 10 minutes. If the s.l.h of vaporisation of nitrogen at its boiling point is 1.99 x 105, at what rate were the surroundings heating the beaker? Why is the heat capacity of the beaker irrelevant?
Ok, my attempt:
Q / T = m / T x L
Q / 600 = 0.0463 / 600 x 1.99 x 105
P = 9213.7 J/s
The reason why the specific heat capacity of the beaker is irrelevant is because during the process, the temperature of the liquid nitrogen does not change and the beaker would already be at the same temperature as its contents due to thermal equilibrium.
2. An open dish of liquid is very slightly cooler than its surroundings. Why? Your answer should include an account of why it's temperature is steady, and the factors which determine the steady temperature.
I believe the reason why the temperature is slightly slower is because of evaporation: The molecules with the most energy are able to escape, leaving only the cooler, less "energetic" molecules behind. I don't understand however, the second part of the question. Could anyone give me any tips?
Thanks,
Peter G.
The mass of liquid nitrogen in an open beaker is found to have decreased by 46.3 g in 10 minutes. If the s.l.h of vaporisation of nitrogen at its boiling point is 1.99 x 105, at what rate were the surroundings heating the beaker? Why is the heat capacity of the beaker irrelevant?
Ok, my attempt:
Q / T = m / T x L
Q / 600 = 0.0463 / 600 x 1.99 x 105
P = 9213.7 J/s
The reason why the specific heat capacity of the beaker is irrelevant is because during the process, the temperature of the liquid nitrogen does not change and the beaker would already be at the same temperature as its contents due to thermal equilibrium.
2. An open dish of liquid is very slightly cooler than its surroundings. Why? Your answer should include an account of why it's temperature is steady, and the factors which determine the steady temperature.
I believe the reason why the temperature is slightly slower is because of evaporation: The molecules with the most energy are able to escape, leaving only the cooler, less "energetic" molecules behind. I don't understand however, the second part of the question. Could anyone give me any tips?
Thanks,
Peter G.