significant figures in pH calculations

Answer 1

Because pH is a log, the number in front of the decimal is not counted in the sig figs. For example, a pH of 4.35 is considered to have 2 sig figs (the 3 and the 5). Does that answer your question?

Answer 2

Hi Julio,

Number of significant figures for pH calculations depends on two factors:

1. Precision of your instrument--if your instrument records pH to 3 sig figs. i.e. 6.99 for tap water, report that way. If you are referring to calculations from textbooks:
2. Use the lowest number of significant figures from the measurements you were given. If you were given pH of one sample of water to be 6.9, and another sample to be 7.02, use two significant figures in your final answer because that is the number in the lowest measurement.

I hope this helps.