How would you determine is the following salts will from a solution that is acidic, basic, or pH neutral? CH3NH3CN, Fe(ClO4)3, K2CO3, CH3NH3CL, RbI
1 Answer
Identify the nature of the salts in an aqueous solution.
Explanation:
Generally, before you try to make an aqueous solution of a salt (basically, dissolving them), you should check against a solubility table.
After this, to calculate the pH of your salt solution, you need to know the concentration of the salt solution, whether the salt is an acidic, basic, or neutral, the equation for the interaction of the ion with the water (an ionic equation helps), the equilibrium expression for this interaction and the Ka or Kb value.
The relationship between Ka and Kb for any conjugate acid-base pairs is:
(Ka)(Kb) = Kw
Where Ka is the ionization constant of the acid form of the pair, Kb is the ionization constant for the base form of the pair, and Kw is the ionization constant for water. This equation is used to find either Ka or Kb when the other is known.
Remember, when certain soluble salts are dissolved in water the resulting solution is not neutral. Depending on the composition of the salt (the ions which it is made up of) the solution will be either acidic or basic. Soluble salts that contain anions derived from weak acids form solutions that are basic. The anion is the conjugate base of a weak acid.
On the other hand, soluble salts that contain cations derived from weak bases form solutions that are acidic. The cation is the conjugate acid of a weak base. For example, the ammonium ion is the conjugate acid of ammonia, a weak base.
Of course, if you have any bottles of Universal Indicator lying around, use them. But that's the simplest way.
