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Hi Prof, if I remember correctly, during the lecture, you mentioned that if an iterative method is being tested, we just need to show the workflow and complete one iteration.

But my question is: if we only do one iteration and we don't get the correct $T_{\text{bubble}}$, we actually cannot get the correct composition of the bubble (vapor phase)? So what shall we do?

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Hi prof, could u pls explain the reason behind the following statement--

(VLE)when the system temperature is higher than the critical temperature of the species, it then has a limited solubility in liquid phase

thx!

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I'm already lost since week 4. should i just drop this mod and take the F grade at this point

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You mentioned that in the Henry's Law question that it can be assumed to be ideal solution due to water's dominance. What would be the red line to say it is or isn't an ideal solution. Like x = 10^-4? 10^-5?

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Hi Prof, in the exam, could you give a hint on the question on what Eqn to use please?   E.g. Hint: Use Henry's Law

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Hi Prof, in the exam, could you give a hint on the question on what Eqn to use please?   E.g. Hint: Use Henry's Law

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Students still require the knowledge of how to use the equation to solve the problem, so it doesn't make the exam too easy also.

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Taking this module inspires me to dropout and apply to McDonalds

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Taking this module inspires me to dropout and apply to McDonalds

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For this question, I calculated γ1 and γ2 using P/Psat. After that, I submitted them into lnγ1 = Ax2^2 and lnγ2 = Ax1^2 and got 2 different values of A. May I know what is wrong?

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Hi Prof Karthiga, I remember that you mentioned that you may be uploading review slides + a video from last year to help us in our Final Exam preparations. Will you still be doing that?

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For this question, I found the answer to be 0.578 bar. My equation is:

Ln[P/P_1^sat]/Ln[P/P_2^sat] = x_1^2/x_2^2

Ln[x/0.7]/Ln[x/1] = (0.371)^2/(0.629)^2

x = 0.578

Only if I change ln(gamma_1) = Ax_1^2 to ln(gamma_1) = Ax_2^2, then I get the correct answer. Is this difference related to my solution or Activity coefficient equation given has error?

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Dear prof,

Are you going to share tutorial 11 problems discussion notes with us?

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Dew temperature calculations with Modified Raoult's Law

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Dew temperature calculations with Modified Raoult's Law

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In the Thursday lecture, we went through Question 5 on using Modified Raoult's Law as the VLE model to calculate bubble and dew pressures. Actually, bubble temperature calculation using Modified Raoult's Law is also rather straightforward if model parameters for the chosen activity coefficient model are given (e.g. constants A12 and A21 for 2-constant Margules). However, dew temperature calculations seem much more difficult using this VLE model because we need to guess temp as well as the composition of the liquid right? Which I don't think an iterative method will allow us to solve and software will become necessary right?

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for a given temperature, can i use the k-factor difference to show that it will flash?

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for a given temperature, can i use the k-factor difference to show that it will flash?

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since K factor shows the tendency to be in certain state, if i find Ki/Kj to be not 1, does that prove the mixture will flash?

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What type of question would require K factor calculation? 

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What type of question would require K factor calculation? 

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Phase Equilibrium-Problem Solving Slide 15 

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Phase Equilibrium-Problem Solving Slide 15 

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Hi prof, just checking if there are errors in the values of y1 and y2? For example, using the equation under point 3), @T=365K, y1 = (0.4*137.834)/100 = 0.551 but the value shown on the slide is 0.4135

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Hi prof, why can we use modified raoult’s law for this question? I thought that this can only be used at VLE @ low P, but we don’t know the P here?

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If we use poynting's equation and lewis randall rule, fugacity of liquid A at azeotropic point will be 0.55*1600=880?

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Prof, could you expl how to determine which is min/max boiling azeotrope?

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Prof, could you expl how to determine which is min/max boiling azeotrope?

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Hi Prof, may I clarify that in the demonstration on phase transformation on both P-xy and T-xy diagram, overall composition of species 1: Z1, means (moles of species 1 in liquid phase + moles of species 1 in vapor phase)/(moles of species 1 in liquid phase + moles of species 1 in vapor phase + moles of species 2 in liquid phase + moles of species 2 in vapor phase)?

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Hi prof, for the 3 different compositions (80%,60% and 20%), is it referring to species 1 or 2? Do we just designate the composition of each loop as the more volatile species?

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For the topmost graph, why are there 2 critical points for the mixture? Which one do we use as the critical point for that mixture?

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Hi prof, just to clarify: the pressure-composition diagram use the more volatile species (1) and shows the composition of species 1's liquid and vapor phases (x1 and y1 respectively). So taking the bubble point B for example:

x1=0.6, x2=0.4

y1=0.74, y2=0.26

Is my current understanding correct?

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Hi prof, for the left axis, did you mean the composition is x1=0 and y1=1 (instead of x2=1)?

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Hi prof I was wondering if the points circled in orange represent anything? Do we just need to know that the the RKAC1 line is the vaporisation curve for species 1 and UBHC2 is the vaporisation curve for species 2? So the points themselves don't represent anything?

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Prof, where can i find a 3d model of the azeotropic diagram which you showed in lecture that can be rotated, i want to see all sides of it, up,down,left,right and i dont trust my imagination

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Prof, where can i find a 3d model of the azeotropic diagram which you showed in lecture that can be rotated, i want to see all sides of it, up,down,left,right and i dont trust my imagination

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Independent variables required to describe the state of the system
F = N - pi + 2

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Equality of chemical potential (or fugacity) of species across all the phases at constant T and P

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Identify single and multi-phase regions at the given conditions

Describe phase transformation

Evaluate composition of single and multi-phases in equilibrium

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Vapourization curve (P-T curve) along which vapour and liquid phases exist in equilibrium.

Critical point: Highest P and T beyond which vapour and liquid phases becomes identical.

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Envelope bounded by saturated liquid (bubble) and saturated vapour (dew) curve.

Bubble point: First bubble of vapour forms from liquid mixture (or) last bubble of vapour condenses into liquid phase.

Dew point: First droplet of liquid forms from vapour mixture (or) last droplet of liquid vapourizes from liquid phase.

Critical point: Composition dependent

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Low pressure; chemically similar mixtures.

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Low pressure; chemically dissimilar

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For species with limited solubility in liquid phase

VLE system T>Tc of the species

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Plots the composition of vapour and liquid phases in equilibrium.

Used to comprehend the ease of separation

For good separation the Ki should be different from 1

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Constant boiling mixtures

Composition of vapour and liquid phases will be equal.

High boiling (or) minimum pressure azeotrope

Low boiling (or) maximum pressure azeotrope

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Evaluate composition of bubble
and
Bubble pressure/temperature

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Evaluate composition of liquid droplet
and
Dew pressure/temperature

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Evaluate composition and amount of vapour and liquid phases in equilibrium

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Also known as minimum pressure azeotrope.
Boils at temperatures higher than its pure species
Formed by mixtures that deviate negatively from ideal solution

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Also known as maximum pressure azeotrope.
Boils at temperatures lower than its pure species
Formed by mixtures that deviate positively from ideal solution

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Why the composition of liquid is same as overall composition at bubble point?
The system comprises a liquid phase in equilibrium with a minute bubble. Mole number of species in the bubble is very small compared to the overall mixture. It is therefore the composition of liquid phase is same as overall composition.

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Why the composition of vapour is same as overall composition at dew point?
The system comprises a vapour mixture in equilibrium with a liquid droplet. Mole number of the liquid phase is very small compared to the overall system. The composition of vapour phase is therefore the same as overall composition.

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Hi Prof! Just to check for questions that use Henry's Law would the Henry's constant be provided?

Yes. Property data will be provided