part a Some salts are basic, meaning that when those salts are dissolved in wate
ID: 552363 • Letter: P
Question
part a
Some salts are basic, meaning that when those salts are dissolved in water, the anion further reacts with water to form a basic solution. A very important example of this is given by reactions of the potassium acetate salt:
C2H3O2-(aq) + H2O(l) HC2H3O2(aq) + OH-(aq)
Not all anions are basic, only those that are the conjugate bases of weak acids. The conjugate bases of strong acids do not affect the pH of a solution, e.g., those anions are neutral.
How should the conjugate base anion of a strong acid change the pH of an aqueous solution?
Since a strong acid ionizes incompletely, its conjugate base will react with water to lower the pH.
Since a strong acid ionizes incompletely, its conjugate base will react with water to raise the pH.
Since a strong acid ionizes completely, its conjugate base is too weak to react with water thus will not change the pH.
Since a strong acid ionizes incompletely, its conjugate base is too weak to react with water thus will not change the pH.
part b
Many cations when dissolved in water will cause the formation of an acidic solution. In this course only one acidic cation is of interest, that is the ammonium cation, NH4+. In the case of this cation, all of its compounds are water soluble as in the following example with ammonium chloride:
NH4+(aq) + H2O(l) H3O+(aq) + NH3(aq)
Why was there no reaction of water to form a basic solution due to the Cl- ion in ammonium chloride above?
Cl- is the very weak conjugate base of the strong acid HCl and will react with water thus increasing the pH.
Cl- is the weak conjugate base of the strong acid HCl and will not react with water thus not changing the pH.
Cl- is the strong conjugate base of the strong acid HCl and will react with water thus decreasing the pH.
Cl- is the very weak conjugate base of the strong acid HCl and will not react with water thus not changing the pH.
part c
Should the Na+ ion or other Group 1 or 2 cations be considered to be acidic cations? Why?
Yes, they are the very weak conjugate acids of strong bases (like NaOH) and as such increase the solution pH.
Yes, they are the strong conjugate acids of strong bases (like NaOH) and as such decrease the solution pH.
No, they are the very weak conjugate acids of strong bases (like NaOH) and as such do not change the solution pH.
Yes, they are the very weak conjugate acids of strong bases (like NaOH) and as such decrease the solution pH.
part d
Some salts are neutral, meaning that when those salts dissolve in water, neither the cation nor the anion cause the pH of the solution to change. These are salts are composed of cations and anions which do not change the pH of an aqueous solution when dissolved. Examples of these include NaCl and CaCl2.
Why should CaCl2 be considered a neutral salt? (Choose all that apply.)
Ca2+ is the weak conjugate acid of the weak bases CaO and Ca(OH)2.
Cl- is the very weak conjugate base of the strong acid HCl.
Ca2+ is the very weak conjugate acid of the strong bases CaO and Ca(OH)2.
Cl- is the weak conjugate base of the weak acid HCl.
Since a strong acid ionizes incompletely, its conjugate base will react with water to lower the pH.
Since a strong acid ionizes incompletely, its conjugate base will react with water to raise the pH.
Since a strong acid ionizes completely, its conjugate base is too weak to react with water thus will not change the pH.
Since a strong acid ionizes incompletely, its conjugate base is too weak to react with water thus will not change the pH.
Explanation / Answer
Part A
Since a strong acid ionizes completely, its conjugate base is too weak to react with water thus will not change the pH.
part B
Cl- is the weak conjugate base of the strong acid HCl and will not react with water thus not changing the pH.
part C
No, they are the very weak conjugate acids of strong bases (like NaOH) and as such do not change the solution pH.
part D
Cl- is the very weak conjugate base of the strong acid HCl.
Ca2+ is the very weak conjugate acid of the strong bases CaO and Ca(OH)2.
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