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pH change in the titration is one of the most common practices in chemistry. While conducting an experiment, it is essential to know the amount of material given. Chemistry students have to usually study the pH change in the titration via different methods such as titration of a strong base using a universal indicator. Or titration of a strong acid using a universal indicator in the experiment.
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Key Terms: Titration, Study the pH change, Universal indicator, experiment, strong base, titrant, nitrate, experimental observation.
Concept of Titration in Chemistry
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Titration is the exact process that allows you to identify the amount of an existing substance and to know its proportion, which is yet unknown to you, in the overall matter. The investigator mixes a known amount of one substance to the unknown amount of one substance. This process of knowing the unknown amount of a substance is named Titration.
Titration
Read more: Catalysts
What is Titration Experiment in Chemistry?
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Titration experiment in chemistry makes it easy to quickly identify the unknown amount of one substance with the reaction taking place. The form of proportion in which the two substances combine is the result. The investigator makes an experimental observation when titrant or titrating reagent is added in the definite amount using a burette with a stop cock.
The point of change in the color of the solution to which the student adds a universal indicator specifies the point of equivalence of the solution. As the titration takes place, there is a slow change in the pH in the immediate stage. On the other hand, when it approaches the equivalence point, there is a very quick change in the pH of the solution.
Read more: Constant Proportion Law
Methods of Performing Titration Experiments
The unknown amount of a substance can be known via performing different methods of titration experiments. There are a total of three titration experiments in chemistry.
Titration experiment can be done with the help of…
- Strong acid with a universal Indicator.
- Strong base with a universal Indicator.
- Strong acid with a strong base
Read more: What are acids and bases?
How to Perform a Titration Experiment?
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One can perform the titration experiment by knowing about the required material, procedure, and precautions. The aim should be already clear to the person doing this experiment of change in the titration of a strong base with a universal indicator.
Aim of Experiment
The aim of this titration experiment is to study the pH change in the titration of a strong base using a universal indicator.
Materials Required for Experiment
One burette, 2 Beakers of 250 ml capacity each, a Conical flask of 100 ml capacity, one Dropper, 25 mL Hydrochloric acid with 0.1 M, a pH chart for reference, 50 mL of Sodium Hydroxide solution with 0.1 M, 2-3 drops of a Universal indicator, a pH chart for reference.
Read more: Which are the types of solutions?
Diagrammatic representation of Pipette and Burette
Setting up Experimental Base for Titration Experiment
For experimental setup, a burette is set on the stand with a stop cock. A conical flask will be kept at the base with a base or acidic indicator in it. Burette would be containing a strong base to which you want to test. One can get an idea of the experimental setup by looking at the image.
Setup for Titration experiment of a strong base with universal indicator
Read More: Concepts in Chemistry
Procedure to Study ph Change in Titration
- Take 25 ml Hydrochloric acid with 0.1 M in the 100 ml Conical flask (kept at the base in the setup).
- Hydrochloric acid was filled in the flask. Now, add a base to the burette. Fill the sodium hydroxide with 0.1 M in the burette.
- Then, add 2-3 drops of universal indicator in the conical flask (kept at the base). Open the stop cock, and keep putting in the base to acid drop by drop. Don't forget to shake the flask simultaneously.
- Do an experimental observation of the content of the flask after adding each drop of sodium hydroxide solution.
- Note the color of the solution in the conical flask each time you add and observe the solution from the burette.
- Find out the pH by comparing its color with the pH chart.
pH chart for reference
- Make a note of your observations in the observation table of the titration experiment. (Sample observations are provided below in the observations section.)
- Now, create a graph of pH and total volume of NaOH from the burette put in.
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Observations
Experimental observation of the whole process is needed. One needs to observe it till the solution reaches its natural point while adding NaOH to HCl. Note the pH change observed during the process of titration experiment of 25 mL of 0.1 M HCl with 0.1 M NaOH (base) solution in the observation table. One needs to note down their observations of pH change in this kind of observation table.
| Sl.no. | Amount of NaOH added in lots (mL) | Amount of NaOH added to the solution in the flask (mL) | pH |
| 1 | 0 | 0 | |
| 2 | 12.5 | 12.5 | |
| 3 | 10.0 | 22.5 | |
| 4 | 2.3 | 24.8 | |
| 5 | 0.1 | 24.9 | |
| 6 | 0.1 | 25.0 | |
| 7 | 0.1 | 25.1 | |
| 8 | 0.1 | 25.2 | |
| 9 | 0.1 | 25.3 | |
| 10 | 0.1 | 25.4 | |
| 11 | 0.5 | 25.9 |
Read more: Rate of chemical reactions
Precautions
- Use a minimum quality of the universal indicator. It should not be more than 5 drops at all.
- Take the strong acid with full cautions.
- Maintain a particular distance from the setup.
Read more: NaOH
Things to Remember
- Titration helps to know the unknown amount of a substance.
- You need to take a substance with a known amount that will be added to the other substance for titration.
- Point of change in the color of the solution to which the student adds a universal indicator specifies the point of equivalence of the solution.
- The aim should be already clear to the person doing this experiment of change in the titration of a strong base with a universal indicator.
- Careful observation needs to be done of this titration experiment.
Sample Questions
Ques: What is titrate? (1 mark)
Ans: Titrate is the solution that has to be titrated. It is generally taken in a conical flask. Hydrochloric acid was the titrate in this experiment.
Ques: What is a titrant? (1 mark)
Ans: Titrant is the solution that is used to carry out the titration. It is generally put up in a burette flask. Sodium Hydroxide was the titrant in the titration experiment of a strong base with a universal indicator.
Ques: What trend of pH change will you observe in the neutralization of strong acid with a strong base? (1 mark)
Ans: The endpoint or equivalence point shall be 7.
Ques: What is the pattern of pH change for neutralization of weak acid (acetic acid) with a strong base (sodium hydroxide) you observe? (1 mark)
Ans: There is an immediate change in the pH value at the end of the reaction in this experiment. It also depends on the salt formed.
Ques: What is the pH range in which the indicator gives a change in color if the HCl is to be neutralized by NaOH? (1 mark)
Ans: There is a need to refer to the graph or pH scale (provided in the image above). Using the titration curve one can find that around the pH range of 7 color change is witnessed.
Ques: How do you know which indicator to use for titration? (3 marks)
Ans: Before starting the titration experiment using any universal indicator, one needs to ensure its pH value range by checking it. The pH value range of a universal indicator should fall within the range of reaction taking place. An example will help to understand and explain this. If one is experimenting with a strong acid and a strong base, the pH will repeatedly change from 3 to 11 just after adding a few drops into it.
The indicator will not depict the pH range outside the reaction. Hence, make sure to take an indicator having a range of 6-10 in such a case. Another example is methyl red, having a pH range of 4 to 6. Therefore, it cannot depict from 1 to 4 and 6 or above. So, an indicator that falls within the pH range should be taken.
Ques: Which Universal Indicator will You Use to Perform Titration in Strong Acid and Weak Base? (3 marks)
Ans: The usually preferred universal indicator to perform a titration experiment between a strong acid and a strong base is the phenolphthalein indicator. The reason behind choosing this indicator is its pH value range that ranges from 8.3 to 10. The phenolphthalein indicator changes its color to clear. Moreover, in basic acidic solutions, it changes its color to pink. Nonetheless, before experimenting using this universal indicator, ensure that both strong acid and strong base must have the same concentration. During the experiment, ensure that you are taking only a few drops of indicator and adding a base to acid drop by drop. As neutralisations can happen within a first few drops.
Ques: How will you define titrate in your terms? (1 mark)
Ans: Titrate is the substance whose quantity is unknown in the process of titration.
Ques: What should be the final pH value for the experiment performed? (1 mark)
Ans: The final pH should be 7 i.e, neutral in pH range.
Ques: What will happen if you perform the same experiment with a strong base and a weak acid? (2 marks)
Ans: The concentration of the acid and the base should be the same. Otherwise, one will not be able to depict and observe the experiment.
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