Thermo Lecture 2

Question 1

What is the 1st Law of Thermodynamics?

Answer 1

dU = dQ + dW

Internal Energy U is a state function

Question 2

What is the source of internal energy to a monatomic ideal gas?

Answer 2

Translational Kinetic Energy

Question 3

What is 1st Law of Thermodynamics when only expansion work is possible?

Answer 3

dU = dQ - PdV

Question 4

What is the heat capacity Cv for an isochoric process? What are the conditions for this to be true?

Answer 4

Cv = (dU/dT)v = (dQ/dT)v

No phase change

Question 5

What is Enthalpy?

Answer 5

Form of energy that accounts for expansion work at constant pressure

Question 6

What is the formula for Enthalpy, H?

Answer 6

H = U + PV

Question 7

Under constant pressure, what is dH equal to?

Answer 7

dHp = dQp

Question 8

What are discontinuous phase transitions?

Answer 8

Feature an observable discontinuity in physical properties. Defined by the presence of latent heat.

Question 9

What is the enthalpy change for the transition from liquid to gas?

Answer 9

ΔH = ΔHliquid + ΔHvaporisation +ΔHgas

Question 10

What is the equation for the enthalpy of a reaction, ΔHreaction?

Answer 10

ΔHreaction = Σνi Hf0i
Equal to the sum of the stoichiometric coefficient multiplied by the enthalpy of formation of each species.
ONLY for when Hf0 temperature is same as ΔHreaction temperature

Question 11

How to you calculate ΔHreaction at any temperature?

Answer 11

ΔHr(T) = ΔHr(Tr) + Σνi Hi
ΔHr(T) = ΔHr(Tr) + ∫ Cp,i dT

Integral between T and Tr

Question 12

If enthalpy of reaction is positive is the reaction endo- or exothermic

Answer 12

endothermic

Question 13

If enthalpy of reaction is negative is the reaction endo- or exothermic

Answer 13

exothermic (heat lost to surroundings)