Physics Question??: A spherical pot of hot coffee contains 0.75L of liquid??

Posted on 2014-11-18 07:13:00 in Physics by SOPHIE

An emissivity of 0.6,and the surroundings are at a temperature of 20C.Calculate the coffee’s rate of heat loss by radiation.

2. A Styrofoam bucket of negligible mass contains 1.75kg of water and 0.45kg of ice. More ice, from a refrigerator at -15C, is added to the mixture in the bucket, and when thermal equilibrium has been reached, the total mass of ice in the bucket is 0.778kg. Assuming no heat exchange with the surroundings, what mass of ice was added?

3. A thirsty nurse cools a 2L bottle of a soft drink (mostly water) by pouring it into a large aluminum mug of mass 0.257kg and adding 0.12kg of ice initially at -15C. If the soft drink and mug are initially at 20C,what is the final temperature of the system,assuming no heat losses?

4. A flask with a volume of 1.5L,provided with a stopcock,contains ethane gas at a temperature of 300K and atmospheric pressure 1.013×10^5Pa.The molar mass of ethane is 30.1g/mol.The system is warmed to a temperature of 380K,with the stopcock open to the atmosphere.The stopcock is then closed,and the flask cooled to its original temperature.What is the final pressure of the ethane in the flask?Find the mass of ethane remaining in the flask.

5. Initially at a temperature of 80C, 0.28m3 of air expands at a constant gauge pressure of 1.38×10^5Pa to a volume of 1.42m3 and then expands further adiabatically to a final volume of 2.27m3 and a final gauge pressure of 2.29×10^4Pa.Compute the total work done by the air. CV for air is 20.8J/(mol?K)

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