Kp = (Pso₂)(Pc∣₂) / Pso₂c∣₂


Let the change in partial pressure of the SO₂Cl₂ be x atm

Draw up the ICE table.

P/atm□□SO₂Cl₂ ⇌ SO₂ + Cl₂

I□□□□□□1.531□□□0□□□0
C□□□□□□ -x□□□□+x□□+x
E□□□□□1.531-x□□ x□□□x

(Ignore the white boxes, they are used for spacing purposes only)


Kp = (x atm)(x atm) / (1.531 - x)atm

5.26×10-² atm = x²/(1.531 - x) atm

5.26×10-² = x²/(1.531 - x)

Since the extent of dissociation of SOSO₂Cl₂ can be assumed to be small,

x ≪ 1.531
So 1.531 - x ≈ 1.531

5.26×10-² ≈ x²/1.531

5.26×10-² × 1.531 ≈ x²

x ≈ √(5.26×10-² × 1.531)

x ≈ 0.2838

x ≈ 0.284 (3s.f)


So at equilibrium,

Pso₂ = Pc∣₂ ≈ 0.284 atm

Pso₂c∣₂ ≈ (1.531 - 0.2838) atm
= 1.2472 atm
= 1.25 atm (3s.f)

Hi Hi. U should discuss with teacher the assumption of X negligible is not valid. withoutassumption still can get X = 0.258 which is not that much smaller than 1.53. Just my opinion. I will not blindly accept this. Hee Hee. Please don't reply as I don't want to be disturbed. G N :)

Lol. It's not up to you to decide if it's acceptable or not.

That is the under the jurisdiction of the Cambridge examiners.

It is common at Singapore A levels H2 Chemistry to do so. The whole point is to save the time of solving a more complicated quadratic equation. It is an accepted way of doing this question. The approximation is also used in questions involving acid/base equilibria .

That being said, since you can't 'blindly accept this' you can always choose to solve it if you want :)

As a Raffles institution student who has been posting A level H2 Chem, Physics and Math questions, you ought to know better.

I'm sure your prestigious school would have told you that :D

And if you choose to comment, others can choose to respond as well. ;)

That's why you r here every day giving essay long solutions trying to explain simple concepts. Take hours to answer simple questions. Good tutor do not need to look for students here. Wonder who will engage such tutor. Accept blindlyto what the system telling you is not what an educator should preach his students.

Yeah. I did post a basic chem qn. And you asked me for model answer!!! what a shame! please don't claim that u can teach a level math n chemistry LA.

That's cute. You calling detailed explanations 'essay long'. But it's okay, other students do appreciate them because they get to clear their doubts and also get to understand the different complications and factors to consider.

If I wanted to just give 'simple' answers to those so-called simple concepts, I could. But would the student actually learn?

Most students ask for detailed explanation here. Maybe just not you.

And no, I don't take hours to answer i.e not slow as you suggest. We are busy people with many students to teach. You should be glad that we actually take out our pockets of free time to help you guys. Answering bit by bit whenever we are free.

And who said anyone is looking for students here? Most of you here are here in the first place because you want free answers, lol. Do you really think anyone can get students here?

Most people who come here will stop contributing answers shortly after when they realise they don't get the returns they want.

There are only a couple of long-timers who consistently post like me, Eric K and AC Lim.

You seem to have the same thinking as Yong Kc that all people are coming here to compete for students. LOL. Wake up your idea la.

We don't get any remuneration from spending our time answering students like you. Writing/typing all these answers is doing goodwill only.

Also, your point on accepting blindly is invalid. The main purpose of the approximation method is to save time. In physics and chemistry, there are so many assumptions and even some major scientific works depend on assuming something is true (eg. Collatz conjecture

So it's not about blindly accepting as you say. The student would already have been explained to about the limitations of such assumptions in class. That is also what I always point out.

Using the approximation method is for convenience at this level. In your H2 syllabi, there are so many assumptions and things that are not really true. You should be aware of them.

So don't come and accuse others of preaching 'accept blindly' when it was simply a case of providing a method that is suitable for this level.

Many years before you, I asked the same question about that assumption to my teachers as well :)

And here's the thing. You posting a basic chem question that nobody wanted to answer. Which was already surprising given your background.

You came to another student's question comments sections to ask me for help.

I asked for the school so we could all save time if you wanted a fast solution to your very basic chem question since I already have a question/answer bank to all those past year prelims.

You tried to suggest that I couldn't do and it's okay, it's too difficult. And then started to make comments like I'm reluctant to help, and I was typing solutions that other students won't read, and I should spend time helping you better.

Since you sounded so desperate and angsty, since you didn't provide the school name, I decided to answer your question anyway from scratch.

Typed out all the answers, and also drew and uploaded the energy level diagram, contributing whenever I had spare pockets of time.

Sadlt, the next thing I see, was you throwing a backhanded compliment saying I took 3 hours to answer just part a).

So it's really funny to see someone like you, unable to do your homework (your questions are pretty simple) and coming here to ask (or beg I should say) and to suggest that I can't teach when I still answered your question anyway.

If you can't even do a simple energetic question on the calcium carbonate decomposition, I worry for you.

Also, making silly comments like those also shows that you're self-entitled and unappreciative. Not being able to appreciate the time and effort others spend on helping you.

Luckily, most other students aren't like you.

You're basically looking for fast and free answers, expecting people to reply you on demand. If you want that kind of dedicated service, go get a tutor! (Or actually ask him/her if you have one!)

Don't complain about others not helping you or being too slow for your liking, or answers being too long for your liking.

Unless, you're too much of a scrooge to actually spend on your education.

You've got much to learn about life, RI kid.
We tutors here already passed our poly/A levels/got our degrees. You haven't. We don't need the help. You do.

We don't owe you anything.

Learn to be humble and appreciative, instead of being smug Don't sully your school name like many smart alecs who came before you did :(