Materials Required :

Citric acid (H₃C₆H₅O₇)

Sodium citrate (Na₃C₆H₅O₇) or trisodium citrate

Distilled or deionized water

pH meter or pH indicator paper

Weighing balance

Calculate the ratio of citric acid and sodium citrate :

Use the Henderson-Hasselbalch equation to find the ratio. Here, this means the concentration of sodium citrate should be 234.5 times the concentration of citric acid for pH 5.5.

Let's assume [Citric Acid] = x M and [Sodium Citrate] = 234.5x M.

[Sodium Citrate] = 234.5 * 0.000212 ≈ 0.0497 M.

Weighing :

For 1L : Molar mass of citric acid (C₆H₈O₇) = 192.13 g/mol

0.000212mol/L×192.13g/mol=0.0407g.

For 1L : Molar mass of sodium citrate (Na₃C₆H₅O₇·2H₂O) = 294.10 g/mol

0.0497mol/L×294.10g/mol=14.63g.

For 1L of 0.05 M citrate buffer at pH 5.5

Dissolve 0.0407 g of citric acid and 14.63 g of sodium citrate in distilled water. Stir the mixture until fully dissolved. Check the pH of the solution using a pH meter. After adjusting the pH, dilute the solution with distilled water to a final volume of 1 liter.

Thank you Sir