Summary of buffer solution

CH3COOH H+ + CH3COO- asam lemah

CH3COONa Na+ + CH3COO-garam asam lemah basa konjugasi

Larutan Penyangga CH3COOH/CH3COO-

Komponen asam CH3COOH dalam larutan penyangga berasal dari asam lemah CH3COOH yang terurai sedikit sekali.Komponen basa CH3COO- dalam larutan penyangga dianggap hanya berasal dari garam asam lemah, CH3COONa yang terurai sempurna.

MEMBUAT LARUTAN PENYANGGA

1. Larutan Penyangga HA/A-

a. Asam Lemah dan Garamnya

b. Asam Lemah Berlebih + Basa Kuat

CH3COOH + NaOH CH3COONa + H2Oasam lemah berlebih basa kuat garam asam lemah

CH3COOH H+ + CH3COO-

asam lemah sisa

CH3COONa Na+ + CH3COO-

garam asam lemah basa konjugasi


Asam lemah CH3COOH berlebih akan bereaksi dengan basa kuat NaOH membentuk garam CH3COONa.- Komponen asam CH3COOH dalam larutan penyangga berasal dari sisa asam lemah

CH3COOH yang hanya terurai sedikit sekali.- Komponen basa CH3COO- dalam larutan penyangga dianggap hanya berasal dari

garam asam lemah, CH3COONa yang terurai sempurna.

c. Garam Asam Lemah Berlebih + Asam Kuat

2. Larutan Penyangga B/BH+

a. Basa Lemah dan Garamnya

CH3COONa + HCl CH3COOH + NaCl Garam asam Asam Asam lemahlemah berlebih kuat

CH3COOH H+ + CH3COO-

asam lemah

CH3COONa Na+ + CH3COO-

garam asam lemah basa konjugasi


Garam asam lemah CH3COONa berlebih akan bereaksi dengan asam kuat HCl membentuk asam lemah CH3COOH.- Komponen asam, CH3COOH dalam larutan penyangga berasal dari asam lemah

CH3COOH yang terurai sedikit sekali.- Komponen basa CH3COO- dalam larutan penyangga dianggap hanya berasal dari

sisa garam asam lemah, CH3COONa yang terurai sempurna.

NH3 + H2O NH4+ + OH-

basa lemah

NH4Cl NH4+ + Cl-

garam basa lemah asam konjugasi

Larutan Penyangga NH3/ NH4

+

- Komponen basa NH3 dalam larutan penyangga berasal dari sisa basa lemah NH3 yang terurai sedikit sekali.

- Komponen asam NH4+ dalam larutan penyangga dianggap hanya berasal dari garam

basa lemah, NH4Cl yang terurai sempurna.

b. Basa Lemah Berlebih + Asam Kuat

c. Garam Basa Berlebih + Basa Kuat

NH3 + HCl NH4Cl basa lemah asam garam basa lemah berlebih kuat


basa lemah sisa

NH4Cl NH4+ + Cl-



+

Basa lemah NH3 berlebih akan bereaksi dengan asam kuat HCl membentuk garam NH4Cl.- Komponen basa NH3 dalam larutan penyangga berasal dari sisa basa lemah NH3

yang terurai sedikit sekali.- Komponen asam NH4

+ dalam larutan penyangga dianggap hanya berasal dari garam basa lemah, NH4Cl yang terurai sempurna.

NH4Cl + NaOH NH4OH + NaCl garam basa lemah basa basa lemah berlebih kuat


basa lemah

NH4Cl NH4+ + Cl-



+

Garam basa lemah NH4Cl berlebih akan bereaksi dengan basa kuat NaOH membentuk basa lemah NH4OH.- Komponen basa NH3 dalam larutan penyangga berasal dari basa lemah NH3 yang

terurai sedikit sekali.- Komponen asam NH4

+ dalam larutan penyangga dianggap hanya berasal dari garam basa lemah, NH4Cl yang terurai sempurna.

SUMMARY OF BUFFER SOLUTION

1. A buffer solution is an aqueous solution that can maintain the pH of a system within a specified range when a small amount of acid or base is added, or when the system is diluted.

2. A buffer solution has acid and base components that generally take the form of conjugate acid-base pairs: weak acid and its conjugate base (HA/A-) or weak base and its conjugate acid (B/BH+).

3. The equilibrium of acid and base components in buffer solutions. Buffer solution HA/A+ is composed of weak acid (HA) and its salt (MA)

HA(aq) H+(aq) + A-

Acid component Base component from weak acid from salt MA

Buffer solution B/BH+ is composed of weak base (B) and its salt (BHA)B(aq) + H2O BH+(aq) + OH-

Base component Acid component from weak base from salt MA

4. The way buffer solutions work upon the addition of a small amount of acid or base or when dilution takes place.

Buffer Solution HA/A- Buffer Solution B/BH+

Adding small amount of acid (H+)

The acid H+ added will be neutralized by the base component, A-.

H+ + A- HA Acid Base component being added of buffer solution

The acid H+ added will be neutralized by the base component, B.

H+ + B BH+

Acid Base component being added of buffer solution

Adding small amount of base (OH-)

The base OH- added will be neutralized by the acid component, HA.

OH- + HA A- + H2O Base Acid component being added of buffer solution

The base OH- added will be neutralized by the acid component, HA.

OH- + HA A- + H2O Base Acid component being added of buffer solution

Dilution (adding H2O)

Dilution will affect the moles of H+ (H3O+) and OH- in the system, which will cause a shift in the buffer solution equilibrium. The effects of dilution can be observed only if the value of Ka is relatively large and the concentrations of the components are very small.

Dilution will affect the moles of H+ (H3O+) and OH- in the system, which will cause a shift in the buffer solution equilibrium. The effects of dilution can be observed only if the value of Kb is relatively large and the concentrations of the components are very small.

5. The buffer capacity of a solution refers to its ability to resist changes in pH upon the addition of acid/base or dilution. The capacity of a buffer solution is determined by the concentrations of the acid and base components and their concentration ratio. The optimum capacity is obtained when the concentrations of the acid and base components are the same or equimolar.

6. Preparing buffer solutions HA/A- and B/BH+


Weak acid + its salt Weak base + its saltExcess weak acid + strong base Excess weak base + strong acidExcess salt of weak acid + strong acid Excess salt of weak base + strong base

7. Important buffer systems in human bodies: haemogobin, phosphate H2PO4-/HPO4

2-, and carbonate H2CO3/HCO3

-.

SUMMARY OF FORMULA

The Henderson-Hasselbach Equation


pH=p Ka−log[HA ]¿¿ pOH=p K b−log

[B ]¿¿

Sumber:

Johari, J.M.C. dan M. Rachmawati. (2010). Chemistry 2B for Senior High School Grade XI Semester 2. Jakarta : Esis – PT. Penerbit Erlangga.

Summary of buffer solution

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