pH+calculations

Calculations involving pH for strong acids/bases:
Use the following equations to perform calculations of pH, [H + ], pOH, or [OH - ] for strong acids or bases:

pH = - log[H + ]

[H + ] = 10 -pH

pOH = - log[OH - ]

[OH - ] = 10 -pOH

pH + pOH = 14.00 (@25 o C)

[H + ] x [OH - ] = 1.00 x 10 -14 (@25 o C)

Example: a 0.010 M solution of NaOH


 * The [OH - ] = 0.010 M


 * Using pOH = - log[OH - ] = -log(0.010), the pOH = 2.00


 * Using pH + pOH = 14.00, pH = 14.00 - 2.00 = 12.00


 * Finally, [H + ] = 10 -pH = 10 -12.00 = 1.00 x 10 -12 M

Calculations of pH, etc. for weak acids or bases:
This method requires the use of the equilibrium concept (I.C.E.) to determine the pH, [H + ], pOH, or [OH - ] for a given acid or base solution.