Second Law of Thermodynamics

Question 1

What is the second law of thermodynamics?

Answer 1

No engine converts all heat to work

Question 2

In the second law of thermodynamics what kind of engines have the same efficiency regardless of construction?

Answer 2

Reversible engine

Question 3

What is the equation of entropy for isothermal conditions?

Answer 3

Delta S = qrev/T

Question 4

What is entropy?

Answer 4

A state function that identifies spontaneous change among permissible changes.

Question 5

What is the Carnot Cycle?

Answer 5

Engine gets some heat from a high temp source then converts it to work. Leftover heat is disposed into a low temp sink

Question 6

Under what condition is the Carnot cycle process in?

Answer 6

Reversible

Question 7

What is the Clausius inequality?

Answer 7

dS greater than or equal to dq/T

Question 8

What is efficiency?

Answer 8

Determines how good the conversion of heat to work is

Question 9

Equations involving efficiency

Answer 9

e = wcycle/q1
e = 1 + q3/q1
e = 1 - Tc/Th

Question 10

Which is spontaneous: Cooling or heating? Explain.

Answer 10

Cooling because delta S of surrounding is greater

Question 11

What is the equation for Entropy of mixing?

Answer 11

delta S = -R E(ni)lnxi

Question 12

What is the minimum and maximum efficiency?

Answer 12

Minimum = 0
Maximum = 0.99 (not 1 because of 2nd Law)

Question 13

When temperature varies what is the equation for entropy?

Answer 13

delta S =C ln Tf/Ti

Question 14

What is the equation for entropy change during phase transition?

Answer 14

delta S = delta H / T

Question 15

What is the equation for Internal Energy (U)?

Answer 15

Delta U = q + w