- 03 Apr, 2021
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EXP 9 CHEM LAB
1. What are salts and from what compounds are they made from?
2. What are the three types of salts, and which ones ionize water in the hydrolysis reaction?
3. What is the expected pH of these three salt types when each ionize in water?
4. What happens when the hydrolysis reaction products are in equilibrium with the reactants?
5. How is this equilibrium condition expressed for the hydrolysis reaction of acidic or basic salt?
6. What are buffers, and what are they made of?
7. What is the role of salts in maintaining the effectivity of buffers?
8. What happens when a base is added to a system with a buffer? Which component of the buffer will react with the added base?
9. What happens when an acid is added to a system with a buffer? Which component of the buffer will react with the added acid?
10. What were the objectives of this experiment?
11. What data did you collect to achieve these objectives? Briefly explain.
12. What were the hazards and what safety precautions did you implement to reduce the risks of these hazards?
II. Results Analysis
A. Data and Calculations
Summarize the important data and attach all graphs here. Or refer the reader to the Data and Calculations section.
B. Discussion
Part I Salt Hydrolysis and Ionization Constant Determination
1. What two commercial products were used to study the properties of salts in this experiment?
2. What active salts/compounds can be found in these two commercial products?
3. What happens when these two salts undergo hydrolysis reaction? Write the balanced reaction equations. Which ions participated in the hydrolysis reaction?
4. What do your pH readings tell about the acidity or basicity of the salts being studied?
5. How did you use the pH results to calculate the hydrolysis ionization constants (Ka or Kb)?
6. What are your calculated Ka or Kb for these two commercial products and comparing your calculated ionization constants, which salt has the higher concentration of ions in solution?
7. Comparing your calculated Ka or Kb to the theoretical Ka or Kb, what is the percent error for each salt?
Part II The Buffer in Lemonade
1. What are the components of the buffer in lemonade drink?
2. How did you determine the effect of buffer in the lemonade drink?
3. What happened when lemonade with sodium hydroxide? Briefly describe the pH curve?
4. What happens at equivalence point on this pH curve?
5. How many moles of sodium hydroxide were used to reach equivalence point?
6. What happened when citric acid was titrated with sodium hydroxide? Briefly describe the pH
curve?
7. What happens at equivalence point on this pH curve?
8. How many moles of sodium hydroxide were used to reach equivalence point?
9. Comparing the number of moles of sodium hydroxide used in lemonade and citric acid titration to reach equivalence point, what does this tell you about the property of the buffer in lemonade in controlling the pH?
10. In both titration curves, what happens to the pH after equivalence point?
11. Which component of the buffer played a role in allowing lemonade to react with more sodium hydroxide before a pH increase was observed?
III. CONCLUSIONS
1. What can you conclude from the pH results when identifying the acidity or basicity of salts solutions?
2. Using the Ka and Kb results, what properties of salt can you infer from these ionization constant values?
3. Comparing the number of moles of sodium hydroxide used in reaching the equivalence point of lemonade and citric acid titrations, what is the scientific explanation for the difference in results?
4. What is the role of the buffer in the lemonade being able to react with more sodium hydroxide without drastically increasing its pH?
5. Comparing your calculated Ka and Kb values to the theoretical values, what could have caused the high error and how could you have avoided it?
6. What is the practical application of salt hydrolysis or buffers? Give one specific example.