# Stoichiometry calculator

Balancer and stoichiometry calculator

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## Equation balancer » chemical reactions

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I have prepared 11 citrate buffer solutions covering pH 4 to 5 in 10 minutes [using Buffer Maker]. My supervisor couldn't believe it is possible!

Ute Becker

Chemical reaction database - is it possible?

This question is asked often enough to be put in the FAQ section, but it is always asked in the context of chemical Equation Balancing and Stoichiometry calculator, so we decided to answer it here.

How convenient it will be to have database of chemical reactions in the EBAS! All you will have to do will be to enter reactants and the program will show what will happen...

The problem is, such database will not work. Or at least - it will not always work, as the real chemical world is pretty complicated.

There are too many factors that can change the outcome of the chemical reaction. Let's take an example - what will happen, when you add ammonia solution to the copper sulfate solution?

Simple answer is - copper will get complexed and the color of the solution will turn dark blue. But another simple answer is - once you've added a small amount of ammonia, the copper hydroxide will precipitate, dissolving later in excess of ammonia. But that's still not the whole truth, as the copper hydroxide is not stable and it decomposes, leaving black copper oxide. So we have three answers:

Cu2+ + 2NH4OH -> Cu(NH3)22+ + 2H2O

Cu2+ + 2NH4OH -> Cu(OH)2 + 2NH4+

Cu2+ + 2NH4OH -> CuO + 2NH4+ + H2O

Which one is correct? All three! Which one really happens depends on how fast the ammonia solution is added, what the concentrations of reagents are, and how hot the solutions are.

Other example - what will happen if you mix permanganate, sulfuric acid, and some chloride? In this case there is even no simple answer - depending on the concentrations of reagents main reaction can be slow decomposition of permanganate to oxygen and manganese dioxide:

4MnO4- + 4H+ -> 4MnO2 + 3O2 + 2H2O

or two different oxidations of Cl- to Cl2:

2MnO4- + 6Cl- + 8H+ -> 2MnO2 + 3Cl2 + 4H2O

2MnO4- + 10Cl- + 16H+ -> 2Mn2+ + 5Cl2 + 8H2O

Complications doesn't stop here, as in the last case it is enough to add excess amount of Mn2+ ions to the solution, to prohibit the Cl- oxidation.

As you see, the simple database must be misleading, as in many cases it is not easy to predict what will happen and the simple answer can be wrong. Database that can be trusted will be huge, costly, and it will have to ask the user about many parameters that he usually doesn't know. So, in many cases instead of clarifying things it will only add to the confusion. That's why we decided against, at least for now.