how do we calculate pH value of a substance?

Asked by  | 1st Jun, 2008, 09:20: PM

Expert Answer:

pH is a measure of the activity of dissolved hydrogen ions (H+),The formula for calculating pH is:

Where αH+ denotes the activity(concentration) of H+ ions, and is dimensionless.

Example:Dissolving the strong acid HCl in water can  be expressed as:

HCl(aq) → H+ + Cl
This means that in a 0.01 mol/L solution of HCl it is approximated that there is a concentration of 0.01 mol/L dissolved hydrogen ions. From above, the pH is: pH = −log10 [H+]:

pH = −log (0.01)

which equals 2.

Answered by  | 16th Jun, 2008, 01:17: AM

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