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Effect of water pH to the pH of sample solution

Dear Sir/Madam:

I would like to know the effect of the water pH to the pH of sample solution? I am trying to see if there would be difference in the pH of starch solution if I use different pH of distilled water to prepare the starch solution. The result was very minimal, ±0.2 Is the result a big deal or not?

Helena de Guzman
- Valenzuela City, Philippines
2002

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2003

pH stands for potential hydrogen, and is a measure of acidity or alkalinity of a solution of water. This scale is logarithmic, with 7.0 as a center-point. A normal scale counts 1, 2, 3, 4,... A logarithmic scale counts 1, 10, 100, 1000, 10000, .... If you are at 7.1, and it switched to 6.9, then it is not a big deal. If you are at 2.0 and it switched to 1.8, then that is a lot! The pH of the water would probably have a lot to do with the pH of your sample solution. The starch may not have much effect on the pH. If you are conducting any kind of scientific test, you should always start with the same pH level of water. Hopefully your distilled water will give you a consistent pH every time.

Since you are using distilled water, it is very pure and probably close to neutral pH, 7. Highly pure water can attack its container and/or absorb molecules in the air and its pH can drift over time. You may want to try reading the pH multiple times and see how repeatable your measurements are.

Tim Neveau
Rochester Hills, Michigan