[bramgo]

I had an exam today of chemistry.

I had to explain how NH₃ is industrially made.

I explained how the Haber Bosch process works.
This is what I said:

N₂+3H₂--> NH₃
To make this balance of N2, H2 and NH3 go to NH3 the pressure should be raised to 250 time the usual atmospheric pressure. And a relatively high temperature is needed. I also explained that a irondioxide katalysator is needed. And I explained the conflict between thermodynamica end kinetica.

I had to explain him this in person and he asked me the following: "Why would there be more NH₃ by raising the pressure?" Personally I had the impression that this is a very stupid question. Because you will not let anything react by making the pressure lower ofcourse! It's only naturally as a liquid or gas is pressed together that it is more likely to be forced to make an exchange in my oppinion. But he told me: "That's not what I wanted to hear. You can take the test again in August."

You know that's what I hate so much about chemistry. You can study it for years, but in the end it's all Bla blablablabla bla bla bla blablabla bla bla. It's based on feeling and experience, not on calculations. This wouldn't have happened to me if it was a Mechanica exam. No fancy stories there, just ideas that get supported by calculations and facts. That's what makes Chemistry so hated amongst young engineering students, it's not lecture like a science, but it's lectured like it's a language. A mathematics on the other hand is no easy task neither, but you can still save yourself with calculations to find the answer in an other way

[Alberto_Kravina]

Because you will not let anything react by making the pressure lower ofcourse!

In some cases it might be possible.
I.E. in a reaction like X ?? Y + Z  you can move the equilibrium to the side of the products (Y and Z) by lowering the pressure.

It's only naturally as a liquid or gas is pressed together that it is more likely to be forced to make an exchange in my oppinion.

...somehow I don't get this

Take a look at this, hope it helps.

[Borek]

Personally I had the impression that this is a very stupid question. Because you will not let anything react by making the pressure lower ofcourse! It's only naturally as a liquid or gas is pressed together that it is more likely to be forced to make an exchange in my oppinion. But he told me: "That's not what I wanted to hear. You can take the test again in August."

Ever heard about Le Chateliers principle? The question was about equilibrium position.

You know that's what I hate so much about chemistry. You can study it for years, but in the end it's all Bla blablablabla bla bla bla blablabla bla bla. It's based on feeling and experience, not on calculations. (...) A mathematics on the other hand is no easy task neither, but you can still save yourself with calculations to find the answer in an other way

You are abusively wrong. It is enough to write the expression for the equilibrium constant to see that increasing pressure moves the equilibrium in this particular case to the right. But it requires KNOWLEDGE which you don't have. No wonder you have failed.

[Will]

N₂+3H₂--> NH₃

I had to explain him this in person and he asked me the following: "Why would there be more NH₃ by raising the pressure?"

The balanced equation is N_2(g) + 3H_2(g) <--> 2NH_3(g)

To be able to answer the question you have to realise that the reaction is in equilibrium and that there are more moles of gas on the reactants side than the products side. Read the link that Alberto mentioned.

You know that's what I hate so much about chemistry. You can study it for years, but in the end it's all Bla blablablabla bla bla bla blablabla bla bla. It's based on feeling and experience, not on calculations. (...) A mathematics on the other hand is no easy task neither, but you can still save yourself with calculations to find the answer in an other way

You are abusively wrong. It is enough to write the expression for the equilibrium constant to see that increasing pressure moves the equilibrium in this particular case to the right. But it requires KNOWLEDGE which you don't have. No wonder you have failed.

Borek you made me laugh sooo much!

[bramgo]

You are abusively wrong. It is enough to write the expression for the equilibrium constant to see that increasing pressure moves the equilibrium in this particular case to the right. But it requires KNOWLEDGE which you don't have. No wonder you have failed.

Ofcourse I don't have knowledge. I didn't have chemistry in the last 5 years. And I only had about 2 year of chemistry before that. In that year of chemistry they told me to memorize about 50 acids and bases (that's all they teached me). It's only normal that I don't have knowledge.

This guy had 5 hours a week to teach me. In the end I had to look up the "le chatelier" principle myself. And I thought I understood it, seems I didn't but now I do. What just frustrates me is that my prof had 5 hours a week to teach me (during 10 weeks), he could have told me. But he kept it secret till the exam to tell me "HA! see you don't understand".

Maybe he expected that I would have done more research during studying. And that's where the problem is! ==> my whole point is, to me as a non-chemistry guy it seemed only natural that you can't make 2 gasses react by lowering pressure (In physics when you lower pressure in a room, that lowers the Force on the surfaces of everything inside it. It pulls everything away from eachother making them fill the room. That's what I meant earlier in my first comment. To me it seemed that by seperating the H's and N's you couldn't make them connect to eachother.) How should I have known that this wasn't the case in chemistry?! For an outsider it looks perfectly normal.

 I learned a lot today ==> To me chemistry is unpredictable. Everything I THINK I know is based on personal interpretations. Well, it's only natural to make personal interpretations when studying something isn't it? But in a science like mathematics I would have been confronted with my mistakes right away. In chemistry it's more "definitions and concepts", ==> more based on feeling and experience than mathematics if you ask me.

Well, hehe :-) sorry for the frustration in my first post. I had to get this off my chest. For me it's really frustrating as I have spend a lot of time studying this topic. I really had the feeling I was prepared for it. But l have to take over my schoolyear because of this, or quit. Chances are that if I take my year over that this prof will just come up with a new creative smart question.

[bramgo]

You are abusively wrong. It is enough to write the expression for the equilibrium constant to see that increasing pressure moves the equilibrium in this particular case to the right. But it requires KNOWLEDGE which you don't have. No wonder you have failed.

I was hesitating at first but actually I DO want to add the following.

A friend of mine is an industrial engineer in the field of chemistry (Master). And he has gained an additional master degree in the university of Gand (Belgium) in the field of Genes technology. In addition to that he is doctorating in the university of Tokyo (japan) at the moment (searching patterns in DNA strings). (For which he had to learn japanese first) Does he lack knowledge too? Cause he agrees with me about my oppinion on Chemistry.

I would even like to go further on this. About 3 months ago I asked him to help me with some redoxequations. He told me he forgot how those worked a long time ago. He explained to me that it is crap to make chemistry look smart. He told me that the only things I need to know is "what goes in, what goes out, and memorize it".

I heard simular stories from another clever "burgerlijk inginieur" (that's a degree only granted in belgium, it's a special class, far higher than master. It's not given in a university but a special science college. Passing as a "burgerlijk inginieur" guarentees that you will reach one or more doctorates after as only geniouses can make it through that.). Just to illustrate that these are REAL scientists. This guy won the international Physics olympiade and was third in the international mathematics olympiade at the age of 18. After that he won several other international prizes. I think this somehow illustrates that many intelligent people seem to have a weakness for the very basics of chemistry.

In short ... Maybe I gave an agressive and abusive impression in my first post, but there's no need to say I have no knowledge. I wonder what makes you so big to think you can afford yourself to point your finger to somebody.

[Dan]

He told me that the only things I need to know is "what goes in, what goes out, and memorize it".

This is loosely true for school standard chemistry, but other than that, it's absolute rubbish. you can only get so far with memory alone, understanding is the key. Some people can do very well, even at degree level by simply memorizing things. I was actually discussing this with my tutor this evening, he has had students who are very good acedemically because they are good at memorizing stuff, but when it comes to actual research, when they have to work out the answers by themselves, they cope very badly.

Chemistry is far from unpredictable if you understand it.

[jdurg]

Exactly.  Chemistry is a LOT like mathematics.  You need to learn the basic formula and equations and have an understanding of how they work in order to solve the more complex problems.  You don't start out in math by learning differential equations.  You learn the basic concepts of numbers, addition, subtraction, etc.  As time goes on, you learn the more complex formulas and functions, and through these formulas and functions you learn how to apply them in numerous situations.  Sure you can just memorize the answers to equations (I.E. you can just learn what goes in and what comes out), but if you don't learn WHY the answer comes out the way it does you can NEVER apply it to any other situation and you never truly learn it.  If someone just learns chemistry by memorizing things and not learning why things happen, then I would fear any time a chemical is placed into their hands as they really haven't "learned" anything.