Ch 5: 4.3.19 Weekly Quiz problem set

Question 1

What heat is associated with 4.12 kg of ice @ -10.9℃ changing to 31.3℃?

Answer 1

481.01 kcal

Question 2

A heat system has 476 kcal of heat in, and 305 kcal of it is work done on the system. What is the change in internal energy?

Answer 2

171 kcal

Question 3

A heat engine has 826 J of lower change in internal energy while 563 J of work is done on the system of the engine. What is the net heat flow?

Answer 3

-263 J

Question 4

A heat engine can convert 728 kJ of heat into 511 kJ of work. What is the thermal efficiency?

Answer 4

70.2%

Question 5

A system with a thermal efficiency of 31.96% has 4,197 cal of heat in. How much work can it do?

Answer 5

1341 cal

Question 6

An engine has operating temperatures of 280℃ and 520℃. What is the ideal efficiency?

Answer 6

30.26%

Question 7

A salesman claims that a heat system of operating temperatures of 177℃ and 354℃ has a thermal efficiency of 49.2%. Is this believable?

Answer 7

28.2%, so no, not believable.