Why would a buffer change pH with dilution?

Question

I made a buffer today of 1M MOBS and made it pH 7.0 by adding KOH. When I diluted it to 10 mM, the pH was 6.1. At 50 mM the pH was 6.5. Any suggestions?

Answer 1

Buffer solutions are most definitely not supposed to change pH when they are diluted. Given this fact, I would suggest that it was the apparatus that you were measuring the pH with that was causing the error.

Alternatively, think of the water that you were diluting it with. Distilled water is appreciably acidic.

Answer 2

good together as you dilute an answer, you're rather lowering the concentration of ions in determination. have confidence of it this form, a concentrated answer has molecules which could be close at the same time and for this reason have a miles better pH. together as you upload distilled water, the molecules unfold added aside and the pH decreases. This comes from the equation pH = -log(understanding). So the dating is, in the journey that your concentration of hydrogen atoms decrease, so does you value for pH.

Answer 3

Well when you dilute a solution, you are basically decreasing the concentration of ions in solution. Think of it this way, a concentrated solution has molecules that are close together and therefore have a higher pH. When you add distilled water, the molecules spread further apart and the pH decreases. This comes from the equation pH = -log(concentration). So the relationship is, if your concentration of hydrogen atoms decrease, so does you value for pH.

Answer 4

everything changes pH when it is diluted. the more you dilute something the weaker the pH gets.