Pink and Green Doodle Hand drawn Science Project Presentation_20250827_205437_0000.pdf

Experiment

1. Presented by:
Diya Thakur
Bhumija Dilwaliya
Anjali Nijhawan
Dipti Shikha
Purnima Rai

2. To prepare 50ml of an acetate buffer solution
having pH-4. 7 at 25°C pipette, dispenser, flask, beaker, stock solutions of
acetic acid and sodium acetate, measuring cylinder,
glass rod

3. BUFFER*: A buffer is a solution that can resist ph change upon addition of an acidic (H+) or
basic (OH-) components. It neutralize the small amount of H+ or OH - ion thus making ph
relatively stable.
It can be :-
(i) Weak acid + salt of weak acid.
(ii) Weak base + salt of Weak base
*PH*:- It refers to as potential of hydrogen. It is quantitative measure of acidity or basicity
of aqueous or other liquid solutions. It ranges from 0 to 14.
*BUFFERING CAPACITY:-*
It is defined as number of moles of an acid or base that has to be added in 1L of buffer to
cause its PH to change by 1 unit. It is denoted by ( β). It is unitless entity.

4. β= n/ΔpH
n= no. of moles of acid/base added per liter of buffer.
ΔpH= difference between initial pH of buffer & pH of buffer after addition of acid/ base.
*BUFFER RANGE :-*
It is the range of pH which is used for the determination of working of buffer successfully by neutralization of
already added acids and base in order to maintain constant pH.
A buffer has an effective pH range of one pH unit on either side of pKa values for weak acid. If pH of buffers
goes out of range, buffer will no longer be effective.
Buffer range = ( pKa value) - 1 to ( pKa value ) + 1.
Buffer solutions are most effective when concentration of the weak acid is equal to that of its conjugate base.
We usually try to choose a buffer with a weak acid that has pKa value close to desired pH of solution.
*Some common buffers are:-*
1. Phosphate buffers
2. Carbonate buffers
3. Tris buffers

5. As the extent of ionization of weak acid or weak
base is low therefore in order to approximate the
pH of these type of solution this equation is used.
*pH = pKₐ + log([A⁻]/[HA])* It is a device use to measure hydrogen ion activity in
solution. The pH responsive electrode is usually
glass and the reference is usually a silver chloride
electrode.

6. 1.Rinse all glassware with distilled water.
2.Pipette out 2.5ml of acetic acid and transfer to a
beaker.
3.Pipette out 2.5ml of sodium acetate into the
same beaker and mix.
4.Add 45ml of water from a measuring cylinder to
the same beaker and mix
5.Using pH meter check if the desired pH was
achieved.
6.Record the final pH and label the prepared
solution.

7. N₁V₁ = N₂V₂
where,
N₁ = normality of stock solution
V₁ = volume of stock solution
N₂ = desired normality
V₂ = volume of desired solution
pH = pKa + log [concentration of salt] / [concentration of acid]

8. pH = pKa + log [conc. of salt] / [conc. of acid]
4.75 = 4.75 + log [x] / [0.1 – x]
0 = log [x] / [0.1 – x]
antilog 0 = [x] / [0.1 – x]
1 = x / (0.1 – x)
x = 0.1 – x
x = 0.05
0.1 – x = 0.05 Calculation for acid
N₁V₁ = N₂V₂
1 × V₁ = 0.05 × 50
V₁ = 2.5 ml
Calculation for salt
N₁V₁ = N₂V₂
1 × V₁ = 0.05 × 50
V₁ = 2.5 ml

9. Volume of acid Volume of salt Volume of water
2.5ml 2.5ml 45ml

10. A 50 mL acetate buffer solution of desired
pH 4.61 at 25 °C was successfully prepared.
The acetate buffer solution of pH 4.7 was
successfully prepared, showing that a weak
acid and its conjugate base can maintain a
nearly constant pH.

11. 1. Use freshly prepared solutions of acetic acid and
sodium acetate to avoid errors due to
decomposition or contamination.
2. Calibrate the pH meter properly with standard
buffer solutions (pH 4.0 and 7.0) before
measurement.
3. Add reagents slowly and with constant stirring to
ensure homogeneity of the buffer solution.