Thermo Lecture 6 Flashcards Preview

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Flashcards in Thermo Lecture 6 Deck (14)
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1
Q

Define ‘Equation of State’

A

An equation showing the relationship between the values of the pressure, volume, and temperature of a quantity of a particular substance.

2
Q

When is the ideal gas law most appropriate?

A

Low pressures (around 1 bar) and high temperatures (above the supercritical temperature)

3
Q

Give the equation for the compressibility factor Z. What is it for?

A

Z = PV/RT
Use to look at how gases deviate from the ideal. It is indicative of the intermolecular forces. (Z<1 implies attractive forces, Z>1 implies repulsive forces)

4
Q

Give Van der Waals EOS (Dont need to remember)

A

(P + a/V^2)(V-b) = RT

5
Q

What is the problem with the Van der Waals EOS? What do we do to overcome this?

A

Below Tc are 3 solutions to the equation at a given P. Cubic function shows an increase in V for an increase in P which doesn’t make sense in reality.
Do a Maxwell Construction where you replace the cubic curve with a straight line.

6
Q

How do we find a critical compressibility factor?

A

Normalise P, V and T using critical values (i.e Pr = P/Pc) and use these values to calculate Z.

7
Q

What are the 2 types of EOS?

A

Empirical and Fundamentally Based EOSs

8
Q

What us an Empirical EOS?

A

One that takes the ideal gas EOS as the starting point and adds fitting parameters e.g. Redlich-Kwong

9
Q

What is a Fundamentally Based EOSs?

A

One that is derived from a theoretical basis and considers molecular interactions as a starting point. e.g. Virial EOS

10
Q

What must EOS for solids include?

A

A consideration for material properties

11
Q

What is magma?

A

An assemblage of melt, suspended solids and dissolved volatiles

12
Q

Define liquidus

A

The temperature above which a material is completely liquid

13
Q

Define solidus

A

The temperature at which melting begins

14
Q

What is the ‘Eutectic point’?

A

The lowest temperature at which liquid is present