Change in pH of Acetic Acid and Ammonium Hydroxide

The solubility of the ionic precipitate diminishes with the introduction of soluble substances in the solution that shares an ion with the precipitate. The common ion impact is interpreted in this way. The common ion action is the concept we use to describe the change in equilibrium brought on by the addition of common ions to a solution.

Weak acid as well as weak base ionisation, which is also reversible, causes this phenomenon. With the introduction of compounds that have similar ions, reactions that result in the precipitate are frequently seen with residue. With the help of the instances explained below, one will be able to grasp how the pH changes when weak acids and bases are used in experiments.

Table of Content

• Aim

• Theory

• Apparatus Required

• Procedure

• Observation

• Result

• Precautions

• Lab Manual Questions

• Viva Questions

• Practical Based Questions

Aim

1. To study the pH change of a weak acid like acetic acid by sodium acetate addition.

2. To study the pH change of a weak base like ammonium hydroxide by ammonium chloride addition.

Apparatus Required

1. pH Paper 

2. Dropper

3. Test Tube Stand

4. Test Tubes 

5. Test Tube Holder 

6. Acetic Acid 

7. Sodium Acetate

8. Ammonium Hydroxide

9. Ammonium Chloride 

10. Watch Glass

11. Glass Rod

Theory

The ionisation of weak acids like acetic acid is modest. The acetate ions concentration rises when sodium acetate is added to acetic acid. The equilibrium (6.3) is shifted backwards by a rise in the acetate ions concentration. This results in a fall in the OH- ions concentration, which raises the pH of the solution.

Ammonium hydroxide partly dissociates and is a weak base. The amount of NH4+ ions rises while ammonium chloride, a powerful electrolyte, is introduced to the ammonium hydroxide. The equilibrium (6.5) moves on the opposite side because of a rise in the NH4+ ions concentration, and the OH- ions concentration decreases. This implies that as OH- ion concentration rises, with a decrease in pH.

The pH Change of a Weak Acid like Acetic Acid by Sodium Acetate Addition

Procedure

1. Add 10 ml of the 0.1 M acetic acid in a clean, dry test tube. Then place a drop of the acetic acid from the test tube on pH paper and record the colour.  Check the recorded colour using the chart paper and record the pH of acetic acid.

2. Then measure 1 g of sodium acetate and add it to the acetic acid test tube. Then shake the test tube until sodium acetate gets completely dissolved with acetic acid. Using pH paper, check the solution's pH.

3. Re-weigh 1 g of sodium acetate, repeat the procedure twice, measure the pH of the solutions and record the change in the pH value.

Observations

The pH Change of a Weak Base like Ammonium Hydroxide by Ammonium Chloride Addition

Procedure

1. Add 10 ml of the 0.1 M ammonium hydroxide in a clean, dry test tube. Then place a drop of the ammonium hydroxide from the test tube on a pH paper and record the colour. Check the recorded colour using the chart paper and record the pH of the solution.

2. Then measure 1.5 g of ammonium chloride and add it to the ammonium hydroxide test tube. Then shake the test tube until ammonium chloride gets completely dissolved with ammonium hydroxide. Using pH paper, check the solution's pH.

3. Re-weigh 1.5 g of ammonium chloride, repeat the procedure twice, measure the pH of the solutions and record the change in the pH value.

Observations

Result

The results of the chemistry experiment on the change in pH of acetic acid and ammonium hydroxide verified that:

• The pH of acetic acid continues to rise with the addition of sodium acetate.

• The pH of ammonium hydroxide continues to decrease with the addition of ammonium chloride.

Precautions

• Handle chemicals and apparatus with caution.

• Every apparatus should be rinsed with distilled water and dried before starting the experiment.

• Be cautious while recording the observations and comparing them to the conventional pH chart.

• Consistently make note of the observations.

• After the completion of the experiment, wash your hands thoroughly.

Lab Manual Questions

1. What is meant by pH scale?

Ans: The concentration of acids as well as bases is measured using the pH scale, which has a range of 0 to 14.

2. Explain about pH paper.

Ans: We can use pH paper to determine whether the solution is neutral, acidic, or basic. Colour will appear whenever a drop of solution is placed on the pH paper whose pH needs to be measured. The pH colour chart is used to evaluate this colour. The usage of universal indicator solution or paper can be used instead of pH paper.

3. What is meant by a universal indicator?

Ans: A combination of pH indicator solutions is known as a universal indicator intended to measure the pH of solutions over a broad range of readings. Upon the universal pH indicator strip, drop a solution. The colour that was generated on the paper corresponds to the typical pH colour chart.

4. How should pH strips be stored?

Ans: pH strips should indeed be kept in sealed vials or bags in a dry, cool area away from direct sunlight. The optimal temperature is 25 degrees Celsius (77F). A temperature region of 20 °C to 30 °C is suitable.

Viva Questions

1. What type of solution is sodium acetate, acid or base?

Ans: Base.

2. What does a solution's pH imply?

Ans: It gauges a solution's acidic or basic strength.

3. Solution A contains a pH of 6, while Solution B contains a pH of 5. Which of the two solutions is more acidic?

Ans: Solution B.

4. Who introduced pH?

Ans: Soren Sorensen.

5. What is a weak acid?

Ans: The acid which releases less number of hydrogen ions.

6. What is a weak base?

Ans: A weak base does not get ionised 100%.

7. What are the applications of pH?

Ans: pH is employed in agriculture, medicine, research labs etc.

8. What colour does a solution possess if the pH level is 9?

Ans: The colour of pH 9 is light blue.

9. Does the weak acid solution pH vary when a common ion is added?

Ans: Yes. The pH begins to rise.

10. What is the pH of water?

Ans: 7-Neutral.

Practical Based Questions

1. What is the 0.1M ammonium acetate pH value?

1. 6

2. 6.04

3. 7

4. 7.04

Ans: The 0.1M ammonium acetate pH value is 7.04.

2. What is the range of pH of ammonium chloride?

1. 2.5-6

2. 3.5-6

3. 4.5-6

4. 5.5-6

Ans: The range of pH of ammonium chloride is 4.5-6.

3. Ammonium hydroxide is which electrolyte?

1. Strong electrolyte

2. Weak electrolyte

3. Neutral

4. None of the three option

Ans: Ammonium hydroxide is a weak electrolyte.

4. What is the pH value of the addition of sodium hydroxide solution to a weak acid?

1. 3

2. 4

3. 5

4. 6

Ans: The addition of sodium hydroxide solution to a weak acid exhibits a pH value of 6.

5. What type of electrolyte is ammonium chloride?

1. Strong

2. Weak

3. Neutral

4. None of the three options

Ans: Ammonium chloride is a strong electrolyte.

6. What is the nature of the solution if a droplet of solution causes the pH paper to turn orange?

1. Acidic

2. Highly acidic

3. Basic 

4. Highly basic

Ans: The nature of the solution if a droplet of solution causes the pH paper to turn orange is acidic.

7. What type of electrolyte is sodium acetate?

1. Strong

2. Weak

3. Neutral

4. None of the three option

Ans: Sodium acetate is a strong electrolyte. 

8. How does distilled water act in chemical laboratories?

1. Indicator

2. Solvent 

3. Universal solvent

4. None of the three options

Ans: Distilled water acts as a universal solvent in chemical laboratories.

9. What are the two colours seen at the pH chart's extremes?

1. Red and green

2. Green and blue

3. Red and blue

4. Blue and Green

Ans: The two colours seen at the pH chart’s extremes are red and blue.

10. What is the pH value of sodium carbonate?

1. 5

2. 6

3. 7

4. Greater than 7

Ans: The pH value of sodium carbonate is greater than 7.

Conclusion

This chemistry experiment on the change in pH of acetic acid and ammonium hydroxide infers that the formation of a salt precipitate is addressed by the experimentally based observation called the weak acid and base experiment. The pH of the acetate ion rises when sodium acetate is added to weak acid (acetic acid) to ionise it. The equilibrium shifts in the other direction and the amount of H3O+ ions in the solution drops, raising its pH. On the contrary, the pH of ammonium hydroxide ion decreases when ammonium chloride is added to the weak base (ammonium hydroxide).