بوهر
01-12-2007, 00:05
اريد ترجمة السؤال والاجابة النموذجية
A 155-g aluminum cylinder is removed from a liquid nitrogen bath, where it has been cooled
to −196 °C. The cylinder is immediately placed in an insulated cup containing 80.0 g of
water at 15.0°C. What is the equilibrium temperature of this system? The average specific
heat of aluminum over this temperature range is 900 J /kg •K or 0.215 cal/g•°C.
This is where we stopped in class, but there is a
problem. If the final temperature is below
freezing, then the water must have released much
of its heat during the freezing process, and the
final equilibrium temperature would be higher.
When one considers the heat absorbed by the
aluminum during the freezing of the water, one
must conclude that much of that heat was
produced by the phase change, and that some or
all of the water is frozen at thermal equilibrium.
For up to 10 points extra credit, find the actual
equilibrium temperature of this system. If that
temperature is equal to 0°C, calculate how many
grams of the water are frozen when thermal
equilibrium is reached. You must show all of your
work and explain your reasoning to earn
maximum credit
A 155-g aluminum cylinder is removed from a liquid nitrogen bath, where it has been cooled
to −196 °C. The cylinder is immediately placed in an insulated cup containing 80.0 g of
water at 15.0°C. What is the equilibrium temperature of this system? The average specific
heat of aluminum over this temperature range is 900 J /kg •K or 0.215 cal/g•°C.
This is where we stopped in class, but there is a
problem. If the final temperature is below
freezing, then the water must have released much
of its heat during the freezing process, and the
final equilibrium temperature would be higher.
When one considers the heat absorbed by the
aluminum during the freezing of the water, one
must conclude that much of that heat was
produced by the phase change, and that some or
all of the water is frozen at thermal equilibrium.
For up to 10 points extra credit, find the actual
equilibrium temperature of this system. If that
temperature is equal to 0°C, calculate how many
grams of the water are frozen when thermal
equilibrium is reached. You must show all of your
work and explain your reasoning to earn
maximum credit