Acids, Bases, and Salts Objectives, guiding questions, conclusions, and final remarks Guiding questions: Marta Garcia Objectives: To become familiar with the chemical properties of acids, bases, and salts. To develop the concept of pH and approximate the pH of common acids and bases. Guiding questions: Why is HCl a stronger acid than CH3COOH? Please answer this question based on the results obtained in this lab. Provide as much evidence as you can. What is the pH of solutions containing NaOH, Na2CO3, NH4Cl, and NH4Cl respectively? Explain your results with chemical reactions. Conclusions: Answers to guiding questions: anant Nist
The Correct Answer and Explanation is:
Guiding Questions and Conclusions
1. Why is HCl a stronger acid than CH₃COOH?
Based on the experimental results, HCl is a stronger acid than CH₃COOH because it dissociates completely in aqueous solution, releasing a higher concentration of hydrogen ions (H⁺). This was evident in the pH measurements during the lab. The pH of the HCl solution was significantly lower than that of CH₃COOH, indicating a higher concentration of H⁺ ions. For example, HCl showed a pH close to 1 while CH₃COOH had a pH closer to 3 or 4. This demonstrates that HCl is a strong acid with complete ionization, whereas acetic acid (CH₃COOH) is a weak acid that only partially ionizes in water.
2. What is the pH of solutions containing NaOH, Na₂CO₃, and NH₄Cl? Explain your results with chemical reactions.
- NaOH: The pH was around 13. NaOH is a strong base that fully dissociates in water to produce hydroxide ions:
NaOH → Na⁺ + OH⁻ - Na₂CO₃: The pH was around 11. Sodium carbonate is a basic salt that forms from a weak acid (H₂CO₃) and a strong base (NaOH). In water, it forms carbonate and bicarbonate ions which react with water to produce OH⁻:
CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻ - NH₄Cl: The pH was around 5. This salt comes from a weak base (NH₃) and a strong acid (HCl). In water, the ammonium ion reacts with water to produce H₃O⁺, making the solution acidic:
NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺
Final Remarks
This experiment demonstrated the chemical behavior of acids, bases, and salts in water. It also reinforced the understanding of pH and the degree of ionization, which are key concepts for predicting acid-base behavior.
