Posted by Billy on .
The pH of a certain acid having a concentration of 0.20 M was measured. The pH was 2.50. Was this a strong or a weak acid?
I answered it is a strong acid because strong acids have a lower pH.
I am just not too sure if there is anything missing in my answer.
Any help would be appreciated.
Your answer may or may not be right. However, the reasoning is incorrect. You know that if a 0.20 M acid is a strong acid that it must ionize completely; therefore, the (H^+) will be 0.2M and the pH will be about 0.7. The pH isn't 0.7 so it must b a weak acid. Does that make sense? A pH of 2.5 is a lower H^+ than pH 0.7 and you would have a lower H^+ for a weak acid.