Compare the pH of Solutions of Hydrochloric Acid and Acetic Acid having the Same Concentration

When we discuss a solution's pH (“potential of hydrogen” or “power of hydrogen”), we are talking about its hydrogen ion concentration. In other words, the pH scale is used to define whether an aqueous solution is basic or acidic. 

The pH of acidic solutions with increased H+ ion concentrations is typically measured to be lower than that of basic or alkaline solutions. The pH of the stomach is 1.3 which is extremely acidic when food enters it. The pH change makes it possible to break down the food and helps with digestion.

Soil pH plays a very important role in soil fertility. The microbiological activity of soil increases if the pH is maintained at the ideal range (5.5–7.5), which will improve the soil nutrient levels and recycling.

Table of Contents

• Aim

• Apparatus Required

• Theory

• Procedure

• pH paper test

• Observation

• Result

• Precautions

• Lab Manual Questions

• Viva Questions

• Practical Based Questions

Aim

To compare the pH of solutions of hydrochloric acid and acetic acid having the same concentration.

Apparatus Required

• 0.1 M HCl 

• 0.1 M CH3COOH

• 0.01M HCl 

• 0.01M CH3COOH

• Test tubes

• Glass rods

• Universal indicator

Theory

Stronger acids can be completely ionised in an aqueous solution and can form hydrogen ions in higher concentrations. A lower concentration of hydrogen ions is produced by a weak acid.

HCl is a strong acid because it completely dissociates into ions.

HCl ↔ H+ + Cl-

CH3COOH is a weak acid because it partially dissociates into its ions.

CH3COOH  ↔ CH3COO- + H+

Learn how to compare the pH of solutions containing strong acid and weak acid at the same concentration.

pH Paper Test

Using a dry and clean dropper, place the sample on the pH paper. Observe how the pH paper's colour changes. Compare the colour acquired on the pH paper to the standard colours.

pH scale

Procedure

• Use measuring cylinders to fill 4 dry test tubes with 5 mL of each solution at varying concentrations.

• Use a dropper to add a couple of drops of universal indicator to each test tube.

• Take note of the test tube's changing colour.

• Using a standard pH indicator chart and the colour of the test tube's solution, compare the results.

• Take note of the solution's pH.

Observations

Result

A solution of the strong acid HCl has a lower pH than a solution of the weak acid CH3COOH with the same concentration.

Precautions

• Avoid breathing acetic acid fumes too much.

• Never inhale direct acetic acid smells.

• Keep the test tube's mouth away from you.

• Take care when handling the test tube.

• Don't add any additional indicators.

• Clean up the pH paper.

• Exactly match the pH paper's colour and the colour of the fluid in the test tube to the pH indicator chart.

Lab Manual Questions

1. Why are acids' concentrations and pHs varied despite being the same?

Ans: Proton donation is more likely in some acids than others. Therefore, despite having the same concentration, an acid that readily donates protons will have a lower pH than an acid that hardly donates protons.

2. How is pH affected by acid concentration?

Ans: The concentration of hydrogen ions (acidity) increases and the pH lowers when acid is added to a solution.

3. Do lower pH values indicate greater acidity?

Ans: The more acidic it is considered to be, the lower the number (0–7). And the more fundamental it is, the higher the number (7 to 14). Even though the pH scale is quite modest, each whole number corresponds to a ten-fold increase in the concentration of either H ions or OH ions.

4. What happens when acetic acid and water are combined?

Ans: A colourless solution is produced when acetic acid and water are combined in equal amounts. Acetic acid is soluble in water because a homogeneous solution forms.

Viva Questions

1. What is pH?

Ans: A solution's acidity can be determined by measuring its pH, which is a measurement of hydrogen ion concentration.

2. Is pH 1 a strong acid?

Ans: The concentration of hydrogen ions in a solution is evaluated by pH. At the categories of concentrations, you often use in the lab, strong acids like hydrochloric acid have a pH between 0 and 1. Whereas the pH of dilute acid is 6.05

3. List of three strong acids.

Ans: The three strong acids are as follows:

• Hydrochloric acid

• Sulphuric acid

• Nitric acid

4. Is Acetic Acid a strong acid?

Ans: Acetic Acid is a weak acid. As it is partially dissociated in water.

5. What is the percentage of Acetic acid in vinegar?

Ans: Acetic acid makes up only 4-5% of vinegar.

6. What impact does dilution have on pH?

Ans: With dilution, the acidic solution's pH rises and dilution lower the pH of the basic solution.

7. What exactly is the universal indicator?

Ans: A universal indication is a combination of numerous indicators with different pH ranges. It is used to draw attention to the colour spectrum caused by pH changes.

8. What is the name of the indicator solution?

Ans: Universal indicator.

9. Why does acetic acid become a strong acid when dissolved in ammonia?

Ans: When dissolving acetic acid in ammonia liquid, which is unable to form a hydrogen bond. Acetic acid entirely dissociates in liquid ammonia, making it a strong acid.

10. Why does HCl have a higher acidity than HF?

Ans: Fluorine is more electronegative than chlorine, and HCl is a stronger acid than HF. The pH of HCl or a pH of a strong acid is 0 to 1

Practical Based Questions

1. Out of the given options, which acid is stronger 

A) Hydro

B) Citric

C) Acetic 

D) Benzoic 

Ans: Hydrochloric acid is a strong acid

2. Which of the following gases is formed when acetic acid reacts with sodium bicarbonate?

A) Sodium

B) Hydrogen

C) Carbon dioxide

D) Nitrogen

Ans: Carbon dioxide gas is formed when acetic acid reacts with sodium bicarbonate.

3. Acetic acid does not dissolve in: 

A) Glycerol

B) Ether

C) Alcohol

D) Carbon disulphide.

Ans: Acetic acid is miscible with alcohol, glycerol, ether and carbon tetrachloride and in carbon disulphide, it is almost insoluble.

4. Why does acetic acid have a higher pH than HCl?

A) Because more hydronium ions in HCl

B) Because less number of hydronium ions in HCl

C) Because more number of hydronium ions in acetic acid

D) Because less number of hydronium ions in acetic acid

Ans: Acetic acid is a weak acid, only part of its molecules can contribute protons to form hydronium ions. Since there are more hydronium ions in the HCl solution than there are in the acetic acid solution, the pH of the HCl solution will be lowered.

5. Which statement is true about weak acids.

A) Completely dissociated in water

B) Partially dissociation in water

C) No reaction observed

D) Very corrosive

Ans: Weak acids are acids that are partially dissociated in water.

6. What is the pH of 1.0 M acetic acid?

A) 11.2

B) 4.2

C) 2.4

D) 6.9

Ans: The pH of a 1.0 M solution is 2.4, meaning that just 0.4% of the acetic acid molecules are dissociated.

7. What is the pH of Vinegar?

A) 9.6

B) 10.8

C) 2.8

D) 3.5

Ans:  The pH of the Vinegar is 3.5

8. Which of the following solutions have the same concentrations

A) Isobaric

B) Isotonic

C) Isothermal

D) Isochoric

Ans: Isotonic Solutions have the same concentrations

9. The correct formula for HNO2 is

A) Nitrous acid

B) Nitric acid

C) Nitrite

D) Nitrate

Ans: The correct formula of HNO2 is nitrous acid.

10. What is the order of pH of 1 N aqueous solutions of HCl, CH3COOH 

A) HCl>CH3COOH

B) HCl=CH3COOH

C) CH3COOH>HCl

D) None of the above

Ans: The strongest acid will have the lowest pH. This implies CH3COOH>HCl is the correct order.

Conclusion

From the above experiment, we can conclude that the pH of a solution of HCl (a strong acid) is lower than that of a solution of CH3COOH (a weak acid) having the same concentration.