The mean ionic activity coefficient decreases with:
(a) Increasing ionic strength
(b) Decreasing ionic strength
(c) Increasing temperature
(d) Increasing pressure
Answer: (a) Increasing ionic strength
According to the Debye-Hückel Limiting Law and experimental observations, the mean ionic activity coefficient generally decreases as the ionic strength of the solution increases. This happens because increased ion-ion interactions in more concentrated solutions cause the ions to be less effective in participating in reactions than their actual concentration suggests, a deviation from ideal behavior.