Contextualization

Stoichiometry is the study of the quantitative relationships between the substances involved in a chemical reaction. This concept is extremely important in chemistry as it provides a precise way to talk about how the reactants and products of a chemical reaction relate to each other. Stoichiometry helps predict quantities and volumes in any chemical reaction, from burning gasoline in a car engine to synthesizing drugs in laboratories.

Not always the reactants used in a chemical reaction are 100% pure. They may contain impurities, which affect the amount of product that can be obtained. This leads us to two main concepts: purity and yield. Purity is the percentage of a particular substance in a sample, and yield is the amount of product that is actually produced in a chemical reaction compared to the amount that could theoretically be produced.

Importance of Stoichiometry - Purity and Yield

Stoichiometry has deep applications in everyday life and industry. Understanding stoichiometry is essential for anyone working in chemistry or related fields, as it is the basis for preparing solutions and for chemical reactions. This includes careers in pharmacy, biology, chemical engineering, and even culinary arts!

Imagine you are a production chemist and need to prepare a solution to produce a medication. You need to know exactly how many grams of each substance to add for the solution to be effective and safe. Or imagine you work in the food industry and need to know how many grams of each ingredient to add to make a batch of cookies. That's stoichiometry in action!

Determining the purity and yield of reactions is crucial, especially in the chemical and pharmaceutical industries. Purity and yield directly affect the safety and effectiveness of the final products. Furthermore, proper assessment of purity and yield can lead to improvements in the production process, reducing costs and environmental impact.

Practical Activity: Mixing Solids and Yield

Project Objective

Develop students' understanding of stoichiometry, purity, and yield through the execution of a simple and safe experimental activity involving the mixing of solids.

Detailed Project Description

Students, divided into groups of 3 to 5 members, will carry out an experiment in which they will weigh different amounts of different solids, mix them, and then filter the mixture to determine the purity and yield of the recovered solids.

Required Materials

• Solids for the mixture (Example: salt and sand)
• Precision balance
• Containers to hold the solids
• Filter paper
• Funnel
• 2 Beakers or flasks

Step by Step

1. Each group of students should weigh an amount X of salt and an amount Y of sand separately and record them.
2. Next, these solids will be mixed in the same container.
3. They will have to dissolve the mixture in water and filter the solution.
4. The sand, which does not dissolve in water, will settle on the filter paper, and the salt will pass through the filter and dissolve in the water.
5. The filter paper with the sand will be left to dry until the next class.
6. In the next class, students should weigh the filter paper with the dry sand and subtract the weight of the filter paper to determine the amount of sand recovered.
7. They will also need to evaporate the water from the dissolved salt and weigh the amount of salt recovered.

Project Deliverables and Writing the Written Document

The final deliverable will be a written report, prepared in collaboration by all group members, detailing the students' experience with the project. The report should be structured as follows:

1. Introduction: At this point, students should explain the concept of stoichiometry, purity, and yield, explain why these concepts are important in chemistry and in the real world, and highlight the objective of this project.
2. Development: Here, students should explain the theory behind the concepts of stoichiometry, purity, and yield, including how these concepts apply to the experiment they conducted. They should also detail the methodology they used in the experiment, and demonstrate and discuss the results obtained.
3. Conclusion: Here, students should reflect on what they learned from the project, emphasizing their practical experience with stoichiometry, purity, and yield. They should also mention the conclusions they drew based on the results of their experiment.
4. Bibliography: Students should list the sources they used as references during the project development. These may include books, internet sites, videos, among others.

Note: The report should be organized, clear, and well-written, in order to highlight the learning and understanding of the concepts of stoichiometry, purity, and yield that each group acquired during the project.