#AcidBaseTitration

#Chemistry

#ExperimentalTechniques

Introduction

• Titrations are a method of analysing the concentration of solutions

• They can determine exactly how much alkali is needed to neutralise a quantity of acid – and vice versa

• You may be asked to perform titration calculations to determine the moles present in a given amount or the concentration / volume required to neutralise an acid or a base

• Titrations can also be used to prepare salts

Apparatus

• 25 cm3 volumetric pipette

• Pipette filler

• 50 cm3 burette

• 250 cm3 conical flask

• Small funnel

• 0.1 mol / dm3 sodium hydroxide solution

• Sulfuric acid of unknown concentration

• A suitable indicator

• Clamp stand, clamp & white tile

Method

1. Use the pipette and pipette filler and place exactly 25 cm3 sodium hydroxide solution into the conical flask

2. Using the funnel, fill the burette with hydrochloric acid placing an empty beaker underneath the tap. Run a small portion of acid through the burette to remove any air bubbles

3. Record the starting point on the burette to the nearest 0.05 cm3

4. Place the conical flask on a white tile so the tip of the burette is inside the flask

5. Add a few drops of a suitable indicator to the solution in the conical flask

6. Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously

7. Quickly close the tap when the end-point is reached 

   • The endpoint is when one drop causes a sharp colour change

8. Record the volume of hydrochloric acid added, in a suitable results table as shown below

   • Make sure your eye is level with the meniscus

9. Repeat the titration with a fresh batch of sodium hydroxide

10. As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour

11. Record the volume to the nearest 0.05 cm3 

12. Repeat until you achieve two concordant results (two results that are within 0.1 cm3 of each other) to increase accuracy