Determine the pH of a 0.0003 M NaOH solution. Your answer must be within ± 0.1%?

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Answer 1 · 2018-05-04T05:17:56

If you really want to do this properly, just don't round until the end...

This is a strong base, so #["OH"^(-)] = ["NaOH"]#. Therefore:

#"pOH" = -log["OH"^(-)] = -log(0.0003) = 3.52_(287875)#

where subscripts indicate digits past a reasonable final digit of uncertainty.

Hence, the #"pH"# at #25^@ "C"# is:

#color(blue)("pH") = 14 - "pOH" = color(blue)(10.48)#

while the exact solution to #8# decimal places is #10.47_(712125)#. This is obviously within #0.1%#:

#(10.48 - 10.47712125)/(10.47712125) xx 100% ~~ 0.03%#