Determining reactants given the products  [ENDORSED]

Science questions not covered in Chem 14A and 14B. Try to limit questions to chemistry (inorganic chemistry, physical chemistry, organic chemistry, biophysical chemistry, biochemistry, materials science, environmental chemistry).

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Determining reactants given the products

Postby 104822659 » Mon Oct 17, 2016 2:14 pm

Is there a definite way to determine the reactants if we are given only the products?

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Re: Determining reactants given the products  [ENDORSED]

Postby Eunnie_Lee_3H » Mon Oct 17, 2016 2:32 pm

I suppose it depends. There are different types of reactions, such as synthesis, decomposition, single replacement, double replacement, etc.

Synthesis: If you're only given a compound, like NaCl, you can guess that the reactants were probably Na and Cl2.

Decomposition: If you're given two elements such as Cu and Cl2 as the product, you can assume that the reactant was probably the compound CuCl2 (once you knew what charge Cu was in this reaction, in this example).

Single replacement: If you're given an element and a compound, such as Cu and MgSO4, you can see that the Cu and Mg probably "switched" in the reaction, which means that the reactants for this reaction were probably Mg and CuSO4 (again, in this example you'd probably have to know the Cu oxidation state).

Double replacement: If you're given two compounds such as NaCl and H2S as your products, you can see that the Na and H probably "switched places," which would mean the reactants to this reaction were probably Na2S and HCl.

Combustion: If you see that your products are H2O, CO2, it probably means that your reaction was a combustion, and thus one of the reactants is always O2. The other reactant is probably something that looks like CxHy (ex: CH4).

I'm sure there are many more (such as acid-base reactions, redox), but these are usually the "basic" types of reactions. Hopefully this made sense and was what you were looking for.

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