1st Law of Thermodynamics: Closed Systems

Question 1

What are assumptions we can make for an ideal gas?

Answer 1

• Particle size is negligibly small
• There are no intermolecular interactions

Question 2

What is the ideal gas equation?

Answer 2

Pv = RT
* P = Pressure
* v = Specific Volume
* R = Gas Constant
* T = Temperature

Question 3

How do we calculate the Gas Constant for an Ideal Gas?

Answer 3

Gas Constant = Universal Gas Constant / Molar Mass
Universal Gas Constant = 8.31447

Question 4

What are the general rules we can use to see if we can treat a gas as ideal?

Answer 4

• The temperature is high compared to the critical point
• The pressure is low compared to the critical point

Question 5

What is the equation for the compressibility factor?

Answer 5

z = Pv / RT

Question 6

What is the compressibilty factor of an ideal gas?

Answer 6

z = 1 for an ideal gas

Question 7

How can we use the compressibility factor to compare the actual and ideal specific volumes?

Answer 7

z = Actual Specific Volume / Ideal Specific Volume
The actual comes from the superheated vapour tables, and the ideal is calculated from the ideal gas equation

Question 8

How do we determine the thermodynamic properties of compressed liquids, samples near the saturation curve, and samples with a pressure lower than the critical point?

Answer 8

• Compressed Liquid:
  v = Constant T is the same as a saturated sample
• Near the Saturation Curve:
  Use property tables
• At a lower pressure than the critical point:
  Use the ideal gas equation

Question 9

What is the moving boundary work?

Answer 9

The work done is the integral of pressure in regards to volume

Question 10

What is specific heat?

Answer 10

The heat required to raise the temperature of a unit mass by 1 degree

Question 11

What are the two types of specific heat?

Answer 11

• Specific heat at constant pressure
• Specific heat at constant specific volume

Question 12

How many properties do we need to completely specify a simple system?

Answer 12

2 independent properties

Question 13

What is the equation of specific heat?

Answer 13

E = m * c * dT

Question 14

What is the relationship between the cp and cv for specific heat capacities?

Answer 14

cp = cv + R where R is the gas constant of the sample

Question 15

What is the cold air assumption?

Answer 15

We assume there is a constant specific heat, with the value chosen being the one at 25 degrees Celcius

Question 16

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