stuff Flashcards
convert from an extensive (V) to an intensive (v)
v = V/m
what is the difference between adiabatic and diathermic? How does this apply to the first law?
adiabatic = no heat transfer (delta U = W) Diathermic = heat transfer
Derive expression work done? what can you say if the reaction is reversible?
consider small change (w = Force x distance) integrate sub in force = pressure x area therefore W = -integral (pext dv) if reversible p ext = p
What is the first law
delta U = q + w (work = - if work done by system)
Learn triple/critical point diagram and saturation dome diagram
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Expression for enthalpy
H = U + PV
What can you say at constant volume?
delta U = q
What can you say at constant pressure?
delta H = q
delta H = U + PV)
= (q - W) + PV
= q - PV + PV
= qRelation between constant volume/pressure heat capacity?
Liquid/solid –> cp = cv
Ideal Gas –> cp = cv + R
Isothermal reversible expansion of an ideal gas?
sub in pv = nRt into work expression
How do you derive an expression for entropy change?
delta S = nRln(V2/V1) and q rev = nRtln(v2/V1)
divide by T –> therefore, delta S = qrev/T
When does a reaction become spontaneous and irreversible?
delta S > 0
Explain the Carnot cycle and draw diagram?
fun
constant pressure phase transition?
q = delta H, therefore delta S = delta H/T
Entropy change of an ideal gas?
delta U = q + w, delta S = qrev/T, constant volume heat capacity
Clausius statement for the 2nd law?
All spontaneous processes are irreversible (eg heat flow from hot to cold spontaneously and irreversibly)
What is the critical point?
the point at which phase boundaries disappear and a liquid and vapour cannot coexist in equilibrium
What is the triple point?
The temperature and pressure where a liquid, solid and vapour can coexist in equilibrium
What is Henrys Law?
amount of dissolved gas is proportional to its partial pressure in the gas phase
What do you have to assume for Raoults Law?
ideal solution (structurally similar)
Ideal gas law question
low pressure. might be better to use equation of state taking into account the fact that it isnt an ideal gas. This is because the intermolecular forces at high pressure would be significant
What is the first law in words?
Energy cannot be created or destroyed
how are work and energy equivalent?
weight falling over a pulley turning a propeller in water
what is enthalpy?
the energy associated with a fluid entering or leaving a sysem
