Procedure Colour Change And Calculations In Strong Base Titration Using Universal Indicator
While performing any experiment, it is important to know the amount of substance present. This titration is the same process that lets you identify the amount of substance present and to know its proportion.
When we mix any other substance to an unknown amount of one substance, it is known as titration. You can quickly identify the unknown amount of one substance with the reaction taking place. The results gained are in the form of proportion in which the two substances mix. An experimental observation is made when titrant or titrating reagent is added in the definite amount using a burette having a stop cock.
Titration Experiment
Suppose you are given a substance or solution with an unknown amount, and your goal is to find the amount of substance available to you, the process of titration is used in such cases. In the experiment, you will be using the known amount of substance or solution and add to that unknown amount. When this universal indicator or titrating reagent brings a change in the solution’s colour, the point of equivalence is reached.
Initially, you will observe a slow change in the shade of the solution. However, be careful when you are about to reach the point of equivalence. The changes observed at that time are very rapid.
Example of Titration
Titration can be done with:
Strong Acid with universal Indicator.
Strong Acid with Strong Base.
Strong Base with Universal Indicator.
Below we will study the titration of a Strong Base using the Universal Indicator experiment.
Performing The Experiment
Aim of the Experiment:
To study the change in pH value with titration of a strong base using universal indicator experiment.
Things Required:
One burette, 2beakers of 250 ml each, a conical flask of 100 ml, 25 ml of Hydrochloric acid with 0.1 M, a dropper, a pH chart, 50 ml of sodium hydroxide solution of 0.1 M, and a universal indicator.
Setting Up Experiment Base:
In the above picture, a burette is set on a stand having a stop cock. A flash is kept at the base having a base or acidic indicator. Burette will be containing a base or acid to which you want to test.
Procedure to Follow:
In the conical flask kept at the base, take Hydrochloric acid with 0.1 M.
As you have taken acid in the flask, add a base to the burette. Add Sodium hydroxide with 0.1 M.
Now add two-three drops of universal indicator in the conical flask kept at the base.
Open the stop cock, and keep adding a base to acid drop by drop. Also, keep shaking the flask simultaneously.
Keep observing the flask and note down if colour change content is observed. Every time you keep adding solution from the burette, keep noting the colour and compare it with the pH value scale.
Note down your observation in the observation table.
Also, plot a final graph for pH V/s for the total volume of NaOH used from the burette.
Observations:
As you keep adding NaOH to HCl, you need to keep observing when it finally reaches its neutral point, with each observation made drop by drop.
The below table is used to note down your NaOH observations used in 25 ml of HCl with both 0.1 M.
Precautions to Take While Performing Titration Experiment:
The concentration of both strong acid and strong base must be the same.
Use the minimum indicator as possible.
Do not open the stop cock at once. Be sure to add a base to acid drop by drop.
What are The Different Viva Voice Questions for Reference?
How will you define titrate in your terms?
What is titrant according to you?
What should be the final pH value for the experiment performed?
What will happen if you perform the same experiment with a strong base and a weak acid?
FAQs on Titration Of A Strong Base Using Universal Indicator Experiment Guide
1. What is titration of a strong base using universal indicator?
Titration of a strong base using universal indicator is a laboratory method used to determine the concentration of a strong base by reacting it with a standard acid and observing a colour change.
- A known concentration of a strong acid (e.g., HCl(aq)) is added from a burette.
- The strong base (e.g., NaOH(aq)) is placed in a conical flask with universal indicator.
- The reaction is a neutralisation: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l).
- The endpoint is detected by a colour change of the universal indicator near pH 7.
2. What is the aim of the strong base titration experiment?
The aim of a strong base titration experiment is to calculate the unknown concentration of the base using a standard acid and the titration formula.
- Measure the volume of acid required to neutralise the base.
- Use the balanced equation (usually 1:1 for strong acid–strong base).
- Apply the formula: M1V1 = M2V2 (for 1:1 reactions).
- Determine the molarity of the strong base.
3. Why is universal indicator used in strong base titration?
Universal indicator is used because it shows a wide range of colours across different pH values, helping to identify when the solution becomes neutral.
- Strong acid–strong base titrations have an equivalence point at pH 7.
- Universal indicator changes from blue/purple (basic) to green (neutral).
- It provides a visual confirmation that neutralisation is complete.
- However, single indicators like phenolphthalein are often more precise for exact endpoint detection.
4. What is the balanced equation for a strong base titration with HCl?
The balanced chemical equation for titrating sodium hydroxide with hydrochloric acid is HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l).
- This is a neutralisation reaction.
- The mole ratio of acid to base is 1:1.
- One mole of HCl reacts with one mole of NaOH.
- This ratio is used in molarity calculations.
5. How do you calculate the concentration of a strong base in titration?
The concentration of a strong base is calculated using the formula MacidVacid = MbaseVbase for a 1:1 neutralisation reaction.
- Step 1: Record volume of acid used (in dm3).
- Step 2: Use known molarity of the acid.
- Step 3: Substitute into the formula.
- Example: If 0.10 mol dm-3 HCl requires 25.0 cm3 to neutralise 25.0 cm3 NaOH, then NaOH concentration = 0.10 mol dm-3.
6. What is the equivalence point in a strong acid–strong base titration?
The equivalence point in a strong acid–strong base titration is the point where moles of acid equal moles of base and the solution is neutral (pH 7).
- Occurs when complete neutralisation has taken place.
- For HCl and NaOH, the solution contains only NaCl(aq) and water.
- At 25°C, the pH at equivalence is approximately 7.
7. What colour change occurs when using universal indicator in strong base titration?
When titrating a strong base with acid using universal indicator, the colour changes from purple/blue (alkaline) to green at neutralisation.
- Strong base initially: pH 11–14 (purple/blue).
- As acid is added: colour shifts through blue to green.
- At equivalence (pH 7): solution becomes green.
- Further acid addition turns the solution yellow/orange (acidic).
8. What apparatus is used in a strong base titration experiment?
A strong base titration experiment typically uses a burette, pipette, conical flask, and universal indicator.
- Burette: holds standard acid solution.
- Pipette: measures a fixed volume of base.
- Conical flask: contains base and indicator.
- White tile: helps observe colour change clearly.
9. Why is a strong acid–strong base titration curve steep at the equivalence point?
A strong acid–strong base titration curve is steep at the equivalence point because a very small addition of acid or base causes a large change in pH near pH 7.
- Both acid and base fully dissociate in water.
- The solution changes rapidly from slightly basic to slightly acidic.
- This sharp vertical region makes endpoint detection easier.
10. What are common errors in titration of a strong base using universal indicator?
Common errors in strong base titration include overshooting the endpoint, incorrect reading of the burette, and misinterpreting the universal indicator colour.
- Adding acid too quickly near the endpoint.
- Not reading the burette at eye level (parallax error).
- Using too much indicator.
- Not repeating the titration to obtain concordant readings.
