pH of Strong Bases
This section covers the calculation of pH for strong bases. Strong bases fully dissociate in water, releasing hydroxide ions OH−. The pH calculation depends on the number of hydroxide ions released by the base.
For monobasic compounds like NaOH, which release one OH- ion, the concentration of OH- equals the base concentration. The pOH is calculated first, then converted to pH:
Formula: pOH = -logOH− = -logbaseconcentration
pH = 14 - pOH
For dibasic compounds like CaOH2, which release two OH- ions, the concentration of OH- is twice the base concentration:
Formula: pOH = -log2×baseconcentration
pH = 14 - pOH
For polybasic compounds releasing n OH- ions, the general formula is:
Formula: pOH = -logn×baseconcentration
pH = 14 - pOH
An example is provided for calculating the pH of 100 mL of 0.1 M NaOH:
Example: For 0.1 M NaOH, pOH = -log0.1 = 1, pH = 14 - 1 = 13
This illustrates the application of pH calculations for strong bases.