Category: chemistry

Chemical Equilibria

Chemical equilibrium, denotes a reaction condition established when it’s a:

  1. Closed system
  2. Reversible reaction
  3. Dynamic (no visible change, but reaction happens in microscopic level)
  4. Rate of forward reaction = backward reaction (rate of forming products = rate of product dissociation)

You have searched for most common equilibrium processes last week. The ones you must really nail are these two processes:

  1. Haber-Bosch‘s ammonia synthesis
  2. Contact process of manufacturing sulfuric acid (why is it named ‘contact process’?)

The above processes are not all consist of equilibrium reactions. Only ONE reaction for each process. Make a note of which reactions they are and the condition (pressure, temperature, catalyst). (psstt… these are usually the conditions asked in your test).

The conditions stated for the manufacture are the optimised ones. Means they may not give the most abundant product, but they are a good trade-off between good yield and cost of process. Very high pressure may give the most gas product yield, but it will be very expensive on maintaining the pressure and more dangerous for the plant’s workers.

Optimisation, or getting the most suitable compromise, works by shifting the equilibrium. Just like when you’re climbing on an escalator that’s moving down. In order to stay in a certain height, you must climb with the same speed as the escalator, but in the opposite direction. And when you want to go to a new height and stay there, you must climb faster first. Then, when you have reached the new height, you will have the same speed as the escalator again.

This works the same with equilibrium reaction. When equilibrium state is reached, the reaction is dynamically stable. Means, it can change. By changing pressure and/or temperature, you can set the reaction to a new equilibrium. The reaction will then move faster toward forward (or backward) position, then stays there in the new equilibrium state. This change of equilibrium state is what we call EQUILIBRIUM SHIFT.

Equilibrium shift works on Le Chatelier’s principle (he’s a French, so make sure you pronounce it right). Make note on what will change equilibrium position (factors affecting equilibrium) and what the effects are. [if you have done this in your last week’s task in library, it will not be something new for you]. “What will happen if you raise the temperature, will you get more or less product?”, for example.

There could be specific terms on when the factors are NOT applicable. For instance, you can’t shift the equilibrium position of reaction if all the reactants are solid.

Your task would be working on the ‘Latihan 4.2’ in your Kimia 2A Erlangga book. To make working on it easier, understanding the ‘Uji Kepahaman’ questions 4-15 will help. Should there be any difficulty, you can ask here or you can always mention me in Twitter through @litachem.

Tweet you later, kids!

Here are worth websites to visit on equilibria (don’t say I didn’t tell you):

More question papers & announcement

Here’s some files of previous year’s progress test. You might need to sort the questions since there are additional questions due to a task I gave and bits of A2-level chemistry.

When there’s more to esterification or polymerization than what you’ve been taught, then it’s an A2. Confirm it to your 2010 syllabus.

Prog test 1_2008 (alkanes ~ aldehydes)

Rem_final test_2008 (inorganic ~ organic chemistry)

quiz_carbonyl_2009

AS-level_review (minus organic chemistry)

I personally think I’ve given loads of question papers. In addition to packs of past papers I’ve given to you before.

So there should be no more questioning “We need more practice”. YOU need to DO the practice. Not me giving out more questions. They’re more than enough now.

Look for it. Download it. And DO. Don’t waste your time by sitting idly in your class waiting for me to tell you to do something. You have tons to work with, already. What you need is STARTING to dwell in them.

You have 2 weeks starting from this Monday (April 26th, 2010) to do extra task or redo some EoC tests to improve your grades. You can ask for the task or EoC question paper to me.

Mind you, if you don’t ask me, I won’t push it to you. I’ll take it as you’re satisfied with your result. Your schooling is your responsibility.

Good luck.

Addendum

Mid_paper1_sem2_0910

Organic Chemistry. The fun has begun.

The fun has started. Organic chemistry! Yes, it’s like the crippled entangled hair with so many carbons, hydrogens and oxygens. Sophisticated, yet interesting with so many variations hold in patterns of homologous series.

I do like organic chemistry very much, as you’ve heard many times before. And it’s not because it’s easy or I’m excel at it. It’s because the dynamic feature. There are loads of organic compounds. And it keeps developing (inorganic compounds as well) with the growth of demand. Medication is just one of the most important finding of organic chemistry usage.

To deal with organic chemistry, you need a lot of patience. For physical chemistry, you are provided with theories for a solid foundation to go through inorganic and organic chemistry. In inorganic chemistry you learn about periodicity and patterns. While in organic chemistry you will find enormous kinds of organic compounds but with some persistence and careful behavior you see the patterns. Popping up, just like you’re playing enigma 😀

My suggestions are:

1. Re-write the structural/displayed formulae of any given problem. It will do you favor to see more clearly about the possibilities.

2. Check and re-check. Isomers may ‘fool’ you at first. Aldehyde and ketone may look the same at a glance.

3. “Ah. Gitu doang. Gue bisa.” This sentence is very valid to liven up yourself, boosting your mood. But toward the lesson, just grab your writing tool & scrap papers and start working on whatever it is. No matter how easy.

4. Repeat. Recite. Recall. Make a helpful summary. Repeat what you’ve done in class. It will help you in recalling what your friends had commented about it. The discussion. The details. You will gain ‘working hours’ in organic chemistry. Which really matters.

5. Be creative. See where the reaction begins and see where it ends. Find paths. Or alternative paths. The possibilities.

6. Have a note. Scrap papers are OK. You have to build the habit of WRITING organic chemistry.

You decide. You wanna hate it, you’ll hate it. You wanna like it, put the effort. Practice always pays.

Last word: enjoy!