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Offline Silicon-32

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predicting inorganic reactions
« on: January 09, 2022, 12:50:15 PM »
Hi, I'm at the end of the first semester of my chemistry bachelor (technical university of Denmark). I'm having a course in inorganic chemistry (with this part of the course being the transition metals), and I’m a bit frustrated. The Majority of what we learn, both from the textbook and from the lectures, is just how very specific reactions will occur. Still, my professor says, that we don't have to memorize all of the reaction as we should be able predict them by rationalizing. But we aren’t really learning methods for the prediction of reactions, mostly just these very specific ones.

In physics for example, you learn to calculate kinetic energy by a formula, and once you know that formula (and the mass and velocity) you can find the kinetic energy of any given object. but with this course, its like We’re learning how to calculate the energy of an object with the mass of 1 kg then 2 kg then 3 kg and so on, instead of learning the actual formula.
we were recently given this question:

write titanium(IV)chloride's reaction with water
looking at this, I can see two possibilities:

1) TiCl4+2H2O => TiO2+4HCl.
2)  TiCl4+4H2O => Ti(OH)4+4HCl

They both obey the octet rule. Its the 1st one that is correct, but what tools/method/knowledge should I use to determine which one will occur?

I would like to have a "golden" collection of methods making me able to determine any reaction. maybe I’m a bit naive for thinking such a thing exists, but my current method of determining which of the two reactions will occur is by guessing
 This is my 1st post here, so I do apologize if posted at the wrong place.


Offline Corribus

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Re: predicting inorganic reactions
« Reply #1 on: January 10, 2022, 10:00:21 AM »
Just because you can write down a molecular formula on paper does not mean the molecule exists (or, if it exists, is the most likely product of a reaction, or is stable, etc.). Admittedly, distinguishing real, likely-to-exist molecules from fantasy molecules takes a bit of experiential knowledge. But certainly in chemistry coursework, questions usually deal with common chemical species. With specific reference to your post: What makes you think Ti(OH)4 even exists? Can you find a wikipedia article on it? If not, that's probably not the reaction the questions is going after.

(This isn't to disregard the spirit of your question. Oxides can be challenging. In the case of titanium, really the only oxide of note is TiO2, despite the fact that in adopt a couple different crystallographic forms. But some other metals - like copper - can adopt different oxidation states, and in some cases oxides - like phosphorous oxide - can be protonated or not. What form dominates under any situation will depend a lot on the conditions under which it is made, the conditions under which it is stored, and individual kinetic and thermodynamic considerations. This is why your "golden" guide doesn't really exist.)
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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