Science Buddies: "Ask an Expert"

Is it safe to mix Hydrogen Peroxide with potassium sulfate?

Safety is important!

Can you tell us a little bit more about the experiment you are doing with these two chemicals? What concentrations of the two chemicals will you be using? How much will you mix?

Audrey

My 8th grade student found an experiment that mixed alcohol with Potassium sulfate,
He wants to change the experiment by adding hydrogen peroxide instead of the alcohol
In an effort to make it more his own. I do not have the original experiment with me, but
will get it from him on Monday, so I can give you more detail.

My students wants to know if adding hydrogen peroxide, a drop at a time to a test tube 3/4 full of potassium sulfate will create the potassium sulfate to crystallize similar to when you add alcohol to potassium sulfate.

What form is the initial potassium sulfate in? Is it an amorphous powder?

To grow anhydrous crystals of potassium sulfate (arcanite) from the amorphous powered form is a physical chemical process and not a chemical reaction that forms different chemical molecules. Potassium sulfate will not disolve in pure ethanol; however, it will disolve in water. The original experiment as you describe used a water / alcohol solvent to disolve the amporphous powder. Because alcohol+water will evaporate faster than pure water, the experiment took advantage of the faster evaporation and the insolubility of potassium sulfate in pure alcohol to cause the crystal form to grow faster.

1) I see no reason why experimenting with hydrogen per-oxide and potassium sulfate is any more dangerous than the original experiment.
2) I have no clue what the actual solubility of K2S04 is in a H2O2+H2O solvent vs pure H2O. My guess is that the 2 H2O2 will break down into O2 and 2 H2O at some rate and the resulting water will eventually evaporate and potassium sulfate will precipitate out. I have no clue if it will form small or large crystals or end up back as a powder once it is dry. My guess is that alcohol is a better choice for growing larger crystals than H2O2.