Contextualization

Saline hydrolysis is an essential topic for understanding many chemical phenomena. It occurs when a salt, after being dissolved in water, reacts with the H+ or OH- ions present in the water even in its pure form, due to autoionization. To understand how this process occurs in detail, we need to have clear some previous concepts such as: acids and bases, salts, acid-base reactions, and pH.

A salt can be composed of a cation derived from a strong base and an anion from a weak acid (or vice versa), or even both ions from weak acids or bases. The ions, in solution, react with water, increasing the concentration of H+ or OH- ions, making it acidic or alkaline, respectively. This is the essence of saline hydrolysis.

This concept is of utmost importance for Environmental Chemistry, Biochemistry, Industrial Chemistry, and many other branches of science. For example, saline hydrolysis is directly responsible for the formation of acid rain or can even influence the rate of corrosion of metallic materials. In Biochemistry, hydrolysis is essential for understanding the acid-base balance in the human body, which is vital for life maintenance.

Furthermore, mastering this topic is fundamental for a good performance on the ENEM exam and in many college entrance exams in the country.

Practical Activity

Activity Title: "Unraveling Saline Hydrolysis: From Theory to Practice"

Project Objective

Through an experimental activity, investigate the acidic or basic nature of various saline solutions. The task will consist of preparing several saline solutions, measuring their pH, and correlating the results with the theory that governs saline hydrolysis.

Detailed Project Description

Students, grouped in teams of 3 to 5, will carry out an experiment to investigate the concept of saline hydrolysis. They will prepare several saline solutions, measure their respective pH, and correlate the results with the theory. In addition, they will work together to solve theoretical exercises involving saline hydrolysis calculations. This process will allow a comprehensive and immersive approach to the concept of saline hydrolysis, promoting both learning and teamwork skills.

Required Materials

• Salts from different acids and bases (NaCl, NH4Cl, Na2CO3, etc.)
• Distilled water
• Beakers
• Glass stirring rods
• pH meters (pH meter or pH test strips)

Detailed Step-by-Step

1. Each group will choose three different salts to work with.
2. For each salt, a solution will be prepared by dissolving the salt in distilled water, with constant stirring.
3. The pH of the solution will be measured and recorded.
4. Based on the theory, students will predict the nature (acidic, basic, or neutral) of the solution and compare it with the results obtained experimentally.
5. In parallel with the experimental part, students will solve theoretical exercises involving saline hydrolysis calculations, which should be explained and solved step by step in the report.
6. The project will last one week, with an estimated two to four hours of work per student.

Project Deliverables

After carrying out the experiment and the theoretical exercises, each group will deliver a detailed report covering the following points:

• Introduction: Description of the concept of saline hydrolysis, its relevance, and real-world applications.
• Development: Theoretical discussion of saline hydrolysis, detailed description of the experiment carried out, and presentation of theoretical and experimental results. The methodology used should be clearly explained.
• Conclusion: Analysis of the results in light of the theory, lessons learned, and reflection on the experience of working in a team.
• Bibliography: Indication of the sources used in the project, whether books, websites, videos, etc. Use the ABNT citation format.