chem HELPPP

[Icejay]

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A solution of potassium acetate(KC2H302) in water is
1. basic because acetic acid molecules are formed
2 basic because KOH molecules are formed
3. acedic because acetic acid is formed
4. acidic because KOH molecules are formed
5. neutral because potassium acetate is a salt.

the marked answer is 1, but i thought it was 2, wouldnt that make more sense?

 

[sailinx]

The solution is basic because,

KCH3COO ---> K+ + CH3COO- (Salt Dissociate) ---- I

CH3OO- + H2O <---> CH3COOH + OH- ----II

Now, K+ and OH- would never combine in H2O to form a molecule (KOH) as KOH is considered a very strong base. In water it will remain dissociate as K+ and OH- ions.

But acetic acid is a weak acid, therefore, it will form CH3COOH based on equation II. Therefore, the
Ans 1 is correct.

 

[boogaking]

why not 3.... since acetic acid is formed... granted it is a weak acid... doesn't that make the solution acidic???? confused?

 

[sailinx]

why not 3.... since acetic acid is formed... granted it is a weak acid... doesn't that make the solution acidic???? confused?

When is any salt an acid, when it can dissociate in water to give H+ but in this case, look whats happening,


CH3OO- + H2O <---> CH3COOH + OH-

Just to elaborate, H2O <---> H+ + OH- (very small quantity dissociate)

So CH3COO- combines with H+ from water to form CH3COOH (i.e. H+ gets consumed by CH3COO- i.e. H+ doesn't exist any more) So, what else is left, obviously OH-. Therefore, the solution is basic (Very little basic as there is not whole lot of OH- either but [OH-] > [H+]). I hope this helps. To clarify, review acid/base salts in your chemistry text book that should help.

 

[gabrielmeraz]

When is any salt an acid, when it can dissociate in water to give H+ but in this case, look whats happening,


CH3OO- + H2O <---> CH3COOH + OH-

Just to elaborate, H2O <---> H+ + OH- (very small quantity dissociate)

So CH3COO- combines with H+ from water to form CH3COOH (i.e. H+ gets consumed by CH3COO- i.e. H+ doesn't exist any more) So, what else is left, obviously OH-. Therefore, the solution is basic (Very little basic as there is not whole lot of OH- either but [OH-] > [H+]). I hope this helps. To clarify, review acid/base salts in your chemistry text book that should help.

Whenever you are across problems like these, look at the final ions left in solution (i.e. OH- as one of the products) this should give an indication of the type of medium (acidic H+ or basic OH-) exists.