PPT Slide

Common-Ion Effect

• Solubility is decreased when a common ion is added. Therefore the equilibrium shifts to the left.

• This is an application of Le Ch’telierís principle, for eg.:

• as F- (from NaF, say) is added, the equilibrium shifts away from the increase.

• Therefore, CaF2(s) is formed and precipitation occurs.

• As NaF is added to the system, the solubility of CaF2 decreases and more precipitate forms.

• What will happen if a large excess of NaF is added?

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