|Solutions Containing Ions Which Do Not
|Cl-, NO3-, Br-,
I-, ClO4- and SO42-
are all the salts of the very strong acids. They are therefore extremely
weak bases.(ie. Kb=0) They do not appreciably affect the acidity
or alkalinity of an aqueous solution. Na+, K+ and Rb+
and any other alkali metal ion also do not affect the water's pH either. The
same is true for the charged ions in Group IIA. Using these generalizations
we can predict that solutions of NaCl, KI, BaCl2 and RbNO3
which are made from the above cations and anions are essentially neutral.
|All other ions tend to cause pH shifts. Cations tend to make
solutions more basic whereas anions tend to bring a solution closer to acidity.
If both weakly dissociated anions and cations are present then the pH will
have to be determined mathematically.
|1. Without making any calculations, predict the relative acidity
(ie, pH is >, < or =7) of these aqueous solutions.
a) 0.1 mol/L KCl
b) 1.0 mol/L K2CO3
c) 0.1 M NH4NO3
d) 0.1 M NaF
e) 1.1 mol/L Na2SO3
|2. For question (e) above do the calculations and prove that the pH is what you predicted.|