Chem I: Determining Acidic, Basic or Neutral Salt

[markelmarcel]

Homework Statement

Predict if the following salts are acidic, basic, neutral or undetermined.

Homework Equations

a. NaOCl

b. NH₄I

c. Sr(ClO₃)₂

d. KCN

The Attempt at a Solution

A. NaClO = Na⁺ and ClO^-
So, if Na⁺ gives up a proton, that would turn it into Na... and make ClO into HClO... and HClO is a strong acid.

B. NH₄I = NH₄⁺ and I^-
So if NH₄⁺ gives up a proton it turns into NH₃ and HI... which is a strong acid.

C. Sr(ClO3)2 = Sr²⁺ and ClO3^-
So if Sr gives away a proton it's left with Sr₊ and ClO3 becomes neutral??

D. KCN = K⁺ and CN^-
K can give up a proton and be K and make CN- have no charge... CN? Neutral?


I know that C is netural but I don't know why and I'm pretty sure I'm right on the two acids, but the last one I think is supposed to be basic, but I don't know how...

 

[symbolipoint]

You must be wrong about NaClO; One would imagine an anion with more oxygens could be for an acidic protonated form, but the ClO^-1 is not from a strong acid. (Hypochlorite).

KCN ?
K+ from strong base, and CN- from weak acid.

 

[markelmarcel]

You must be wrong about NaClO; One would imagine an anion with more oxygens could be for an acidic protonated form, but the ClO^-1 is not from a strong acid. (Hypochlorite).

KCN ?
K+ from strong base, and CN- from weak acid.

See... I don't understand how this works. Haha. I got one at least! My prof went through all this a little too fast for me. Any online resources to help me better understand this? (I like to be active with learning, not a whiner who just wants the answers)

 

[symbolipoint]

Originally Posted by symbolipoint:

You must be wrong about NaClO; One would imagine an anion with more oxygens could be for an acidic protonated form, but the ClO-1 is not from a strong acid. (Hypochlorite).

KCN ?
K+ from strong base, and CN- from weak acid.

Reply from markelmarcel:

See... I don't understand how this works. Haha. I got one at least! My prof went through all this a little too fast for me. Any online resources to help me better understand this? (I like to be active with learning, not a whiner who just wants the answers)

You do not need internet resources. Your textbook should have plenty of instructive discussion on acid-base chemistry. You will learn which acids are strong and which bases are strong. The rest are nearly always weak acids or bases. The ion of a weak acid or base will tend to hydrolize to recombine with the acid or base from which it is part.

As example, let Ac stand for "acetate" anion. If NaAc is dissolved in water, the salt ions are present in solution as ions; but some portion of Ac will recombine with H+ by hydrolysis:
Ac- + HOH <--------> HAc + OH-

That will tend to make the solution alkaline.