Question

The pH value of a particular weak acid is 6.79; calculate the hydrogen ion concentration for this acid.

Answer 1

The information is that the pH=6.79.
I suggest you memorize the formulas below unless you have a reference sheet:
\(-log[H_3O^+]=pH\)
\(10^{-pH}=[H_3O^+]\)
\(-log[OH^-]=pOH\)
\(10^{-pOH}=[OH^-]\)
\(K_w=[OH^-][H_3O^+]=1×10^{-14}\)...at 25°C
\(pOH+pH=14\) at 25°C
There are a few more equilibrium formulas and the H-H equation. Most of the formulas I listed above are derivable. If you remember formulas 1, 3, and 5, you can derive the rest if you know logarithm rules.

Anways we can use this formula:
\(10^{-pH}=[H_3O^+]\)
pH=6.79
\(10^{-6.79}\)
You can plug that into your calculator and figure it out

Answer 2

btw H3O+ is the same as H+

Answer 3

thank you