Does ethylene dissolved in water affect pH?

Answer

Dear Anne-Mie,

The short answer to your question is simple, ie no, ethylene has no influence on the pH if it were dissolved in water. Now there are several reasons for this. Firstly, the solubility of ethylene in water is quite low, ie 200 mg/L at 15°C. Now that is a solution of 0.02 weight percent which is very low and from there you would expect a small effect on pH. More importantly, ethylene is an extremely weak acid and also an extremely weak base. For clarity, the pH reflects the concentration of acidic protons in water. In pure water this is something of the order of 10^-7 mol/L and that leads to a pH of 7. To change the pH you need a substance that either releases acidic protons (=an acid) itself and that would lower the value of pH (for example pH=3), or a substance that can bind acidic protons (= a base) and that would then raise the pH (for example pH = 10). Given that ethylene is both a very weak acid and a very weak base, the pH will therefore remain unchanged.

I hope you can continue with this.

Regards

Dirk