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Is there a general way to predict products of a chemical reaction, given only the atomic masses of masses of all elements involved? for example:

  1. $\ce{CuFeS2 + O2->}$

  2. $\ce{K2CrO4 + H2SO4->}$

  3. $\ce{FeOCr2O3 + K2CO3 + O2->}$

  4. $\ce{K2Cr2O7 + H2SO4->}$

If there's no method to do so, are we supposed to memorize all chemical reactions?

PS: In case you are writing the mechanism of chemical reactions, please bear in mind that products are not known beforehand.

Hashir Omer
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    Buy a textbook on inorganic chemistry is my advice. It'll give you the basic knowledge about periodicity in the periodic table to know intuitively how a certain element is likely to react. The subject is too vast to answer here. –  Mar 03 '14 at 07:50
  • As @Brian has stated, this is a very broad request - there are a lot of factors to consider, depending on many factors in the reactants, conditions, temperatures, catalysts etc. This resource could be a good start. Take the time to learn this kind of things - it is an enjoyable process! –  Mar 03 '14 at 08:41
  • @ Brian, I would be grateful if you name the book – Hashir Omer Mar 03 '14 at 09:47
  • @ Brian: Is there any general method to predict the products at advanced level? – Hashir Omer Mar 03 '14 at 09:57
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    The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation. -- P. A. M. Dirac – user26143 Mar 03 '14 at 12:35
  • The question based on the incorrect assumption that reactions can be fully predicted based on only elements involved or must be all memorized - excluding any other options – Greg Feb 19 '17 at 12:09

3 Answers3

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Often times it is possible due to previous data. Trends appear and you can make deductions from such trends. Reactions may not happen at all. There may be deviations from the trends as well. The deviations may be for unknown reasons or there may be unproven theories that are included in textbooks. Inorganic chemistry reactions are not as clear cut as organic chemistry reactions. You don't have to memorize all the reactions. Know the trends, conduct the experiment, and if your prediction fails, try to think hard about the conditions in which the experiment took place. Sometimes the explanation may lay in the container that you used for the reaction, or it may be stoichiometry.

As in all sciences, you need experiments.

CoffeeIsLife
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3

Is there a general way to predict products of a chemical reaction, given only the atomic masses of masses of all elements involved?

Unforturnately, no.

If there's no method to do so, are we supposed to memorize all chemical reactions?

There is some amount of reactions one have to memorize individually. However, there are classes of reactions that are quite broad and have uniform rules to check if some reactions happens. Two most common of such classes are redox reactions in solutions, guarded by electrode potentials, and ionic reactions in solutions, guarded by compound solubility expressed as solubility product.

In your example

$\ce{CuFeS2 + O2 ->}$

Is an example of oxidation of sulfides. Most sulfides can be oxidized at elevated temperature by oxygen into stable oxides, in this case (if there is excess oxygen): $$\ce{CuFeS2 + O2 -> CuO + Fe2O3 + SO2}$$

$\ce{K2CrO4 + H2SO4 ->}$

$\ce{K2Cr2O7 + H2SO4 ->}$

Both reactions are ionic and guarded by relative acidity of chromic and sulfuric acids and led to formation of chromic anhydride.

The remaining reaction is unlikely to proceed at significant rate, as the oxide considered is kinetically inert. However, if it would react, the products would be potassium chromate (VI) and later ferrate (VI).

Community
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permeakra
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You can predict certain types of chemical reactions using formats.

  • Combination reaction: $\ce{A + B -> AB}$, for example $\ce{C + O2 -> CO2}$
  • Displacement reaction: $\ce{AB + C -> AC + B}$, for example $\ce{H2SO4 + Zn -> ZnSO4 + H2 }$
  • Double Displacement reaction: $\ce{AB + CD -> AD + BC}$ , for example $\ce{Pb(NO3)2 + 2KI -> PbI2 + 2KNO3}$
  • Decomposition reaction: $\ce{ABC ->[\Delta T] A + B + C}$ [using heat], for example $\ce{CaCO3 ->[\Delta T] CaO + CO2}$ [using heat]

For redox reactions, I am still working

Martin - マーチン
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Abhishek Mhatre
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