BUFFER SOLUTION Is a solution which has ability to maintain its PH value constant on either addition of acid or base provided that its buffering capacity is not exceeded.
Acidic buffer solution Is prepared from reaction btn weak acid and strong salts of the same acid,for example ,The mixture containing acetic acid(CH3COOH) and sodium acetate(CH3COONa),is an example of acidic buffer solution
Basic buffer solution
Is prepared from the reaction btn weak base and strong salt of the same base,forexample A mixture containing ammonium chloride(NH4Cl),is a basic buffer solution.
MECHANISM OF HOW BUFFER SOLUTIONS WORK TO MAINTAIN THEIR PH VALUE
At first Acetic acid in its aqueous solution dissociates partially to give small amount of H ions. CH3COOH -------- CH3COO ions and H Ions
When the sodium acetate is added into Acetic acid solution CH3COONa ------- CH3COO ions and Na ions Ionization of CH3COONa increases the acetate ions (CH3COOions) in the solution. Therefore the increase in CH3COO ions by CH3COOH will cause the equilibrium of Acetic acid to shift more backward hence lead to formation of CH3COOH, Because CH3COO ions will react with Ions of H, being formed from dissociation of Acetic acid originally. The new equilibrium will be re established which H ions that remain after establishment of new equilibrium will be the one which determines, the PH of the resulting buffer solution and must remain constant since the PH value of the buffer solution has to remain un changed.
Worked examples on buffer solution
1. What will happen to the PH of buffer solution if acidic solution like HCL,is added into acidic buffer solution. solution
CH3COOH --------- CH3COOions and Hions CH3COONa ---------- CH3COOions and Na ions HCL ------------ H ions and CL ions The H ions being released by Hcl will disturb the dynamic equilibrium position of CH3COOH .In this case the equilibrium has to move backward to form more acid,since H ions become combined with CH3COO ions of salts to form acetic acid. The PH value of acidic solution will remain fairly constant due to the new re established equilibrium.
2. What happens when NaoH becomes added into Acetic buffer solution? solution
CH3COOH -------- CH3COO ions and H ions
CH3COONa --------- CH3COO ions and Na ions NaOH ------------ Na ions and OH ions
OH ions released by NaOH,combine with H ions from original CH3COOH to form water,hense causing more acid to dissociate therefore make the equilibrium to move this will result into decrease of concentration of acetic acid.
Attempt this question below
3. What is the role of weak acid like CH3COOH in Acidic buffer solution or weak base(NH4OH) In basic buffer solution?
PH EQUATION FOR BUFFER SOLUTION
ACIDIC BUFFER SOLUTION Consider dissociation of acetic acid
CH3COOH------------CH3COO ions and H ion
NOTE we shall continue with this part after you understand the first part.
BUFFER SOLUTION
ReplyDeleteIs a solution which has ability to maintain its PH value constant on either addition of acid or base provided that its buffering capacity is not exceeded.
TYPES OF BUFFER SOLUTION
1 Acidic buffer solution PH>7
2 Basic buffer solutions PH<7
PREPARATION OF BUFFER SOLUTION
Acidic buffer solution
Is prepared from reaction btn weak acid and strong salts of the same acid,for example ,The mixture containing acetic acid(CH3COOH) and sodium acetate(CH3COONa),is an example of acidic buffer solution
Basic buffer solution
Is prepared from the reaction btn weak base and strong salt of the same base,forexample A mixture containing ammonium chloride(NH4Cl),is a basic buffer solution.
MECHANISM OF HOW BUFFER SOLUTIONS WORK TO MAINTAIN THEIR PH VALUE
At first Acetic acid in its aqueous solution dissociates partially to give small amount of H ions.
CH3COOH -------- CH3COO ions and H Ions
When the sodium acetate is added into Acetic acid solution
CH3COONa ------- CH3COO ions and Na ions
Ionization of CH3COONa increases the acetate ions (CH3COOions) in the solution.
Therefore the increase in CH3COO ions by CH3COOH will cause the equilibrium of Acetic acid to shift more backward hence lead to formation of CH3COOH, Because CH3COO ions will react with Ions of H, being formed from dissociation of Acetic acid originally.
The new equilibrium will be re established which H ions that remain after establishment of new equilibrium will be the one which determines, the PH of the resulting buffer solution and must remain constant since the PH value of the buffer solution has to remain un changed.
Worked examples on buffer solution
1. What will happen to the PH of buffer solution if acidic solution like HCL,is added into acidic buffer solution.
solution
CH3COOH --------- CH3COOions and Hions
CH3COONa ---------- CH3COOions and Na ions
HCL ------------ H ions and CL ions
The H ions being released by Hcl will disturb the dynamic equilibrium position of CH3COOH .In this case the equilibrium has to move backward to form more acid,since H ions become combined with CH3COO ions of salts to form acetic acid.
The PH value of acidic solution will remain fairly constant due to the new re established equilibrium.
2. What happens when NaoH becomes added into Acetic buffer solution?
solution
CH3COOH -------- CH3COO ions and H ions
CH3COONa --------- CH3COO ions and Na ions
NaOH ------------ Na ions and OH ions
OH ions released by NaOH,combine with H ions from original CH3COOH to form water,hense causing more acid to dissociate therefore make the equilibrium to move this will result into decrease of concentration of acetic acid.
Attempt this question below
3. What is the role of weak acid like CH3COOH in Acidic buffer solution or weak base(NH4OH) In basic buffer solution?
PH EQUATION FOR BUFFER SOLUTION
ACIDIC BUFFER SOLUTION
Consider dissociation of acetic acid
CH3COOH------------CH3COO ions and H ion
NOTE we shall continue with this part after you understand the first part.