Acidic Reactions Of Ethanoic Acid 165th

[Chemical Engineering Laboratory I]

SEGi University ACIDIC REACTIONS OF ETHANOIC ACID Candidate’s Name: Kee Tze San Student ID: SUKD1601886 Group Number: 2 Group Member’s Name: 1. Chow Yee Lin

SUKD1502359

2. Tan Xin Ren

SUKD1500882

3. Tan Jee Yuen

SUKD1600614

Lecturer/ Supervisor: Ms. Nazlina bt Zulbaldi Date of Experiment: 14.11.2016 Date of Submission: 21.11.2016

1.0 Abstract The objective of this experiment is to identify acidic reactions of ethanoic acid when reacted with strong alkali, metal carbonates and metals. This can be done by preparing eight test tubes. Three test tubes contained 2 cm depth of ethanoic acid solution of 0.05M and the other three test tubes contained 2 cm depth of hydrochloric acid of 0.05M. Full range Universal indicator solution was added to one of the ethanoic acid test tube and one of the hydrochloric acid test tubes. The pH was noted based on the color range provided by the Universal indicator. 0.5 cm depth of sodium carbonate solution of 0.4M was place in a small beaker. Dropping pipette was use to add one drop of the sodium carbonate solution to the ethanoic acid tube which contains the indicator. The solution was stirred using a glass rod then observations were recorded. Drops were added again until the pH turns neutral. The number of drops were counted and noted. These procedures were repeated by replacing sodium carbonate solution of 0.4M with sodium hydroxide. For the reaction of ethanoic acid with metals, a small piece of magnesium ribbon was added to the remaining hydrochloric acid tube. The gas produced was identified. This step was repeated by adding the small magnesium ribbon into the remaining ethanoic acid tube. Both reactions were then recorded and compared. Lastly, 1cm depth of hydrochloric acid solution and ethanoic acid solution was poured into two more test tubes. A small amount of solid copper carbonate was added into the two test tubes and the solutions were stirred using a glass rod until nothing further reaction happens. The observation of the reaction was recorded. Generally, at the end of the experiment, the results obtained were that the reaction of hydrochloric acid with weak alkali, strong alkali and metals were faster than that of ethanoic acid. The details of the results were tabulated tables as shown in the results section of this report. As for the errors made in this experiment, it will be explained in the discussion section of this report.

2.0 Theory/Introduction Hydrochloric acid is a strong mineral acid whereas ethanoic acid is a weak acid. It can be found naturally in the digestive organs of human which is the stomach. Hydrochloric acid is widely used in the industrial field and it helps breaks down food in the stomach. Ethanoic acid or also known as acetic acid is as a weak acid. Vinegar is a main component of ethanoic acid. This

acid is widely used as an organic solvent and to preserve food such as pickles. Since hydrochloric acid is a stronger acid compared to ethanoic acid, it has lower pH value than that of ethanoic acid. Hydrochloric acid has a pH value of 1 while ethanoic acid has a pH value of 3. To neutralize hydrochloric acid, lesser amount of alkaline are needed as it is about 8 times more acidic than ethanoic acid.

Hydrochloric acid will fizz strongly when reacted with metal carbonate solution while ethanoic acid will fizz weakly when reacted with metal carbonate solutions. This shows that the reaction of hydrochloric acid is much more vigorous compared to ethanoic acid. When both acids were reacted with metal, they produce hydrogen gas. This can be tested with a glowing wooden splinter. The flame goes off when exposed to hydrogen gas and you’ll hear a squeaky pop sound produced in the test tube. However, the rate of hydrogen gas produced when ethanoic acid reacts with metal is slower than that of hydrochloric acid.

Since ethanoic acid is a weak acid, it dissociates partially in water to produce ions. The equations of the dissociation of ethanoic acid are shown below: CH3COOH

H+ + CH3COO-

Hydrochloric acid is a strong acid, therefore it dissociates fully in water to produce ions. The equation of the dissociation of hydrochloric acid is shown below: HCl → H+ + Cl Based on the equations above, it is clear that even if both acids have the same molarity; hydrochloric acid will still have higher concentration of hydrogen ions than ethanoic acid. Therefore the pH in hydrochloric acid is lower and it has higher reactivity than that of ethanoic

acid. When alkalis are added, however, the ethanoic acid equilibrium position moves to the right, so eventually all the acid reacts as shown in the equations below: NaOH + HCl

NaCl + H2O

NaOH + CH3COOH

CH3COONa + H2O

Na2CO3 + 2HCl

2NaCl + CO2 + H2O

Na2CO3 + 2CH3COOH Mg + 2HCl

2CH3COONa + CO2 + H2O

MgCl2 + H2

Mg + 2CH3COOH

CuCO3 + 2HCl

(CH3COO)2Mg + H2

CuCl2 + CO2 + H2O

CuCO3 + 2CH3COOH

(CH3COO)2Cu + CO2 + H2O

3.0 Apparatus and Material 

Apparatus 1. Test tube rack 2. 8 test tubes 3. Beakers (2) 4. Glass rod 5. Universal indicator pH 6. Spatula 7. Filter paper



Materials 1. Magnesium ribbon, two 1cm strips 2. Ethanoic acid solution, 0.05M, 15ml 3. Hydrochloric acid solution, 0.05M, 15ml 4. Sodium hydroxide solution, 0.4M, 5ml 5. Sodium carbonate solution, 0.4M, 5ml

6. Copper carbonate, 0.5g

4.0 Procedures 1. A test tube rack containing six test tubes was set up. 2. 2cm depth of ethanoic acid solution (0.05M) was added into three of the tubes. 3. 2cm depth of hydrochloric acid solution (0.05M) was added into the other three tubes. 4. Three drops of full range Universal indicator solution were added to one of the ethanoic acid tubes and the pH was noted. 5. Three drops of full range Universal indicator solution were added to one of the hydrochloric acid tubes and the pH was noted. 6. About 0.5cm depth of sodium carbonate (0.4M) solution was placed in a small beaker. 7. One drop of sodium carbonate solution was added into the ethanoic acid tube which contains the indicator using a dropping pipette. The tube was stirred with a glass rod and the observations were noted. Drops were continuously added until the pH is neutral. The number of drops used was counted. 8. The procedure in step 7 was repeated but sodium carbonate was added to the tube containing hydrochloric acid and indicator instead. 9. Sodium hydroxide solution (0.4M) was added to ethanoic acid and hydrochloric acid. This procedure is done by following the procedure in 5, 6, 7 and 8 but sodium hydroxide was used instead of sodium carbonate. 10. A small piece of magnesium ribbon was added to the remaining hydrochloric acid tube. The gas liberated was identified and recorded. 11. Step 10 was repeated using the third ethanoic acid tube. The rate of reaction was compared with that of hydrochloric acid. 12. A small amount of solid copper carbonate was taken on a filter paper. 13. 1cm depth of hydrochloric acid and ethanoic acid were poured respectively into two more test tubes. 14. The copper carbonate was added to each tube in a very small quantity, a glass rod was used to stir until nothing further happens. Observations were recorded.

5.0 Results Reaction with sodium carbonate Observations

Hydrochloric acid solution

Ethanoic acid solution

(0.05M)

(0.05M)

pH

4

5

Changes after one drop of

No changes

No changes

7

9

sodium carbonate Number of drops of sodium carbonate until pH is neutral

Reaction with sodium hydroxide Observations

Hydrochloric acid solution

Ethanoic acid solution

(0.05M)

(0.05M)

pH

4

5

Changes after one drop of

No changes

No changes

10

13

sodium hydroxide Number of drops of sodium hydroxide until pH is neutral

Reaction with magnesium ribbon Observations

Hydrochloric acid solution

Ethanoic acid solution

(0.05M)

(0.05M)

Reactivity with magnesium

Vigorous, formation of

ribbon

bubbles

Gas liberated

Hydrogen gas

Less vigorous

Hydrogen gas

Reaction with copper carbonate Observations

Hydrochloric acid solution

Ethanoic acid solution

(0.05M)

(0.05M)

Reactivity with copper

Green color solution turns

Copper carbonate powder did

carbonate

colorless

not dissolve completely in solution

6.0 Discussion The main purpose of this experiment is to identify the acidic reactions of ethanoic acid when reacted with strong alkali, weak alkali, metal carbonates and metals. Reactions involved when mixing the chemicals with hydrochloric acid and ethanoic acid were neutralization. Neutralization is a process when acid is reacted with a base; it forms water and salt as its products. However, there are different types of neutralization. Firstly, in this experiment, sodium carbonate was reacted with hydrochloric acid and ethanoic acid. After one drop of sodium carbonate was added into these two acids, the pH of both acids did not change. In hydrochloric acid, 7 drops were required to neutralize the acid. Neutralization is reached when the solution turns from red to green/blue. The products formed at the end of this reaction were sodium chloride, carbon dioxide gas and water. Whereas in ethanoic acid, 9 drops were needed to neutralize the acid. Neutralization is reached when the solution turns from orange to green/blue and the products formed were sodium ethanoate, carbon dioxide gas and water. Carbon dioxide gas was liberated due to the carbonate compound present in sodium carbonate. Comparing the results of these two acids, ethanoic acid needed more number of drops of sodium carbonate compared to hydrochloric acid. This shows that ethanoic acid reacts slower than hydrochloric acid as it is a weak acid.

Figure 1

Figure 2

Figure 1 shows the color of ethanoic acid (left) and hydrochloric acid (right) when full range universal indicator was added into the test tubes. Figure 2 shows the color of ethanoic acid (left) and the color of hydrochloric acid (right) at the point of neutralization when drops of sodium carbonate were added. When both acids were reacted with one drop of sodium hydroxide, a strong base, ethanoic acid and hydrochloric acid showed no changes. The number of drops required to neutralize ethanoic acid were 13 drops. The color of the acid turned from orange to green/blue at the point of neutralization. Products formed in this reaction were sodium ethanoate and water. As for hydrochloric acid, the number of drops required was 10 drops to neutralize the acid. The solution turned from red to green/blue when reached the point of neutralization. The products formed were sodium chloride and water. Like the reaction of ethanoic acid and hydrochloric acid with sodium carbonate, the ethanoic acid takes more drops of sodium hydroxide to neutralize as it is a weak acid. This shows that the reaction of hydrochloric acid is faster than ethanoic acid.

Figure 3

Figure 4

Figure 3 shows the color of ethanoic acid (left) and hydrochloric acid (right) when full range universal indicator was added into the test tubes. Figure 3 shows the color of ethanoic acid (left) and the color of hydrochloric acid (right) at the point of neutralization when drops of sodium hydroxide were added. When a small piece of magnesium ribbon was added into the test tube of ethanoic acid, it was observed that there was a weak fizz in the reaction. Liberation of bubbles in the solution shows that there was hydrogen gas produced during the reaction. The fizz was weak in this reaction. The observation found in ethanoic acid when a small quantity of copper carbonate was added into ethanoic acid was that the powder did not dissolve completely in the solution when stir vigorously. When a small piece of magnesium ribbon was added into the test tube of hydrochloric acid, there was a strong fizz in the reaction. The reaction was vigorous and there were gas bubbles liberated at a fast rate in the hydrochloric test tube. The gas bubbles liberated were hydrogen gas. The observation found in hydrochloric acid when a small quantity of copper carbonate was added into ethanoic acid was that the solution turns colorless when stir gently. Based on the observation made in the two reactions involving magnesium ribbon and copper

carbonate, the rate of reaction between the strong acid of hydrochloric acid and weak acid of ethanoic acid is that the stronger acid has faster reaction than that of a weak acid. The reaction in hydrochloric acid (strong acid) was more vigorous as you can observe when it was reacted with magnesium ribbon. As for ethanoic acid, the reaction is weaker when reacted with magnesium ribbon. The solution of hydrochloric acid reacted completely with copper carbonate faster than ethanoic acid at a given time. This is because there was still powder left in the ethanoic acid test tube despite being stirred vigorously. The outcome of the experiment was favorable. The observations recorded are as what we predicted to observe when the experiment was carried out. However, there were some errors made when this experiment was conducted. Firstly, the color of the ethanoic acid and hydrochloric acid was hard to distinguish. Both solutions have similar shades of red. Therefore it is hard to note the pH of each acidic solution. This can be overcome by using a pH meter for a more accurate pH reading of the acid. When the acidic solution nearly reaches the neutralization point, the color changes were drastic from one drop to another. It is better if a metered pH indicator can be used to note the pH value of the dripped solution. Then, the amount of drops used for neutralization can be averaged based on the approximation value obtained from the reading of the pH indicator. For better and accurate results, it is best to duplicate the results by repeating the experiment for at least three times. 7.0 Conclusion In conclusion, the experiment was successful. The reaction of ethanoic acid with sodium carbonate was slower than that of hydrochloric acid with sodium carbonate as ethanoic acid needed more drop (9 drops) of sodium carbonate to neutralize the acid compared to hydrochloric acid (7 drops). In the reaction of ethanoic acid with sodium hydroxide, more drops of sodium hydroxide (13 drops) were needed to neutralize the acid whereas hydrochloric acid only needed 10 drops to neutralize. This shows that hydrochloric acid neutralizes faster than ethanoic acid. When ethanoic acid reacts with a small piece of magnesium ribbon, the reaction was less vigorous compared while the reaction in hydrochloric acid was more vigorous. The reaction between hydrochloric acid with copper carbonate was faster as the small amount of powder added into the test tube reacted and dissolve completely in hydrochloric acid. In contrast to that, small amount of copper carbonate powder were left unreacted in ethanoic acid at a given time

similar to hydrochloric acid. Based on the results summarize above, we can conclude that the weak acid, ethanoic aid has slower reaction compared to hydrochloric acid which is a strong acid. 8.0 References 1. En.wikipedia.org. (2016). Hydrochloric acid. [online] Available at: https://en.wikipedia.org/wiki/Hydrochloric_acid [Accessed 20 Nov. 2016]. 2. En.wikipedia.org. (2016). Acetic acid. [online] Available at: https://en.wikipedia.org/wiki/Acetic_acid [Accessed 20 Nov. 2016]. 3. Bishop, M. (2016). Weak Acid Equilibrium. [online] Chiral Publishing Company. Available at: http://preparatorychemistry.com/Bishop_weak_acid_Equilibrium.htm [Accessed 20 Nov. 2016]. 4. Sussexvt.k12.de.us. (2016). Acid-Base Reactions. [online] Sussex Tech School District A National School of Excellence. Available at: http://www.sussexvt.k12.de.us/science/chemical%20reactions/acid-base%20reaction.htm [Accessed 20 Nov. 2016].