Acetic acid, CH3CO2H, is the active ingredient in vinegar. It's often abbreviated "HOAc". Vinegar is acidic because acetic acid makes H3O+ when it partially ionizes in water:
HOAc(aq) + H2O H3O+(aq) + OAc–(aq)
Suppose that you have a solution of acetic acid in water that is in equilibrium. How will the acidity of this solution change if you do each of these things to it?
(a) Add more acetic acid (HOAc)
The solution will become less acidic (i.e. [H+] will decrease).
The solution will become more acidic (i.e. [H+] will increase).
The acidity of the solution will not change.
(b) Add sodium acetate (NaOAc)
The solution will become less acidic.
The acidity of the solution will not change.
The solution will become more acidic.
(c) Add NaCl
The solution will become less acidic.
The solution will become more acidic.
The acidity of the solution will not change.
(d) Add Ag+(aq), which reacts with acetate ions to make a precipitate: Ag+(aq) + OAc–(aq) AgOAc(s)
The solution will become more acidic.
The acidity of the solution will not change.
The solution will become less acidic.
a)more acidic?
b)less acidic?
c)will noit chnage
d)less
All of these are problems that you solve with Le Chatelier's Principle. In not so eloquent terms this principle says that a system in equilibrium will shift so as to try to undo what we do to it.
I'll help you get started with one or two.
b. Also can be HAc.
HOAc + H2O ==> H^+ + OAc^-
If you add NaOAc, which ionizes as Na^+ + OAc^-, you have added OAc ions to the HOAc equilibrium. The system will shift to try to use the added OAc^-. It wil shift to the left, which reduces OAc^- and it reduces H^+ at the same time. It also increases HOAc.
d. HOAc ==> H^+ + OAc^-
Add Ag^+ + OAc^- to form AgOAc ppt. That means you have removed OAc^- from solution, the reaction will shift to form more OAc^-; therefore, (HOAc) is smaller, (H^+) is larger.
thanks! were my c and a correct?
I didn't see an answer for a and c. (or any of the others)
at the bottom i put a)more acidic?
b)less acidic?
c)will noit chnage
d)less
a) The acidity of the solution will not change.
Adding more acetic acid (HOAc) to the solution will not change its acidity. This is because increasing the concentration of the acetic acid will not affect the equilibrium between the acetic acid and its partially ionized forms. The reaction will simply shift to the left to maintain the equilibrium and the concentration of H+ ions, which determine acidity, will remain the same.
b) The solution will become less acidic.
Adding sodium acetate (NaOAc) to the solution will decrease its acidity. Sodium acetate is a salt that dissociates in water to form acetate ions (OAc-) and sodium ions (Na+). The acetate ions react with H3O+ ions in the solution, consuming them and shifting the equilibrium to the left. As a result, the concentration of H+ ions, which determine acidity, will decrease and the solution will become less acidic.
c) The acidity of the solution will not change.
Adding NaCl (sodium chloride) to the solution will not affect its acidity. NaCl dissociates into sodium ions (Na+) and chloride ions (Cl-) in water. These ions do not participate in the equilibrium reaction between the acetic acid and water. Therefore, the concentration of H+ ions, which determine acidity, will remain unchanged and the solution will not become more or less acidic.
d) The solution will become less acidic.
Adding Ag+ ions (silver ions) to the solution will decrease its acidity. The Ag+ ions react with the acetate ions (OAc-) in the solution to form a precipitate of silver acetate (AgOAc). This reaction reduces the concentration of OAc- ions, shifting the equilibrium to the right to produce more acetate ions and H3O+ ions. As a result, the concentration of H+ ions, which determine acidity, will increase and the solution will become less acidic.