Contextualization

Stoichiometry, a subfield of chemistry, is essential in understanding how chemical reactions occur. If you have ever wondered why reactions are represented by equations with numerical coefficients (for example, 2 H2 + O2 -> 2 H2O) and not just by their constituents (for example, H2 + O2 -> H2O), if you have wondered how we calculate the amount of a product that will be formed in a chemical reaction or how we determine the limiting reactant in a reaction, then you have encountered stoichiometry.

Stoichiometry is based on the conservation of matter, specifically on Lavoisier's Law, which states that matter is neither created nor destroyed in a chemical reaction. It takes into account the proportions in which elements combine, allowing to predict the amount of product(s) that will be formed in a chemical reaction from a certain number of mole(s) of reactant(s). Stoichiometry also allows determining which of the reactants is the limiting one, that is, the one that will be exhausted first in the reaction, and which one will be in excess, that is, what will remain after the reaction.

Our world is full of chemical reactions; they occur in our bodies, in the kitchen, in the manufacturing of products, in energy production, and much more. Stoichiometry, being the tool through which we understand and predict these reactions, is therefore extremely relevant. Understanding how to calculate the amount of product formed or the amount of necessary reactant is vital in various industries, such as pharmaceuticals, food, cosmetics, among others, where the precise amount of ingredient is required to maintain the quality and effectiveness of the product.

The knowledge of stoichiometry is essential not only for future chemists but also for anyone who wants to better understand the world around them. It is an essential skill for anyone wishing to pursue a career in sciences, engineering, medicine, pharmacy, and other related fields.

Some resources that can help better understand the subject are:

1. Stoichiometry: understand how to perform stoichiometric calculations
2. Stoichiometry: How to perform stoichiometric calculations
3. Video: Stoichiometry - What it is and how to use stoichiometry in chemical calculations

Practical Activity: Simulation of a Chemical Products Factory

Project Objective

The objective of this project is to apply the concepts of stoichiometry, particularly limiting reactant and excess reactant, in a real-life scenario, the production of a chemical product in a factory. Students will have the practice of establishing chemical reactions, identifying the limiting and excess reactants, calculating the amount of product formed, and reflecting on the practical implications of these calculations.

Project Description

Each group of students (3 to 5 students) will represent a company that produces a specific chemical product. They will have at their disposal a limited amount of reactants and will be responsible for determining the amount of product they can produce with these resources.

Students should research and choose a chemical reaction that produces a product of economic relevance (for example, sulfuric acid manufacturing, biodiesel production, soap manufacturing, alcohol fermentation, etc.). After that, they should identify the necessary reactants and determine the quantities they have available.

Required Materials

• Writing materials (pencil, eraser, notebook)
• Calculator
• Internet access for research
• Specific software or applications that can help visualize and better understand chemical reactions (for example, chemical reaction simulators)

Project Step by Step

1. Research and choose a chemical reaction of economic relevance. The reaction should have at least two reactants and one product.
2. Identify the reactants and clarify the proportions in which they combine to produce the desired product.
3. Imagine you have a limited amount of each reactant. Decide on the quantities and record them.
4. If the available amount of reactants is not sufficient to react completely, identify which reactant will be the limiting one and which will be in excess.
5. Calculate the amount of product that can be formed with the available amount of limiting reactant.
6. Discuss the practical implications of having an excess reactant and how this can affect production efficiency and product cost.
7. Discuss how understanding stoichiometry and the ability to identify the limiting reactant and calculate the amount of product formed can benefit the industry, considering economic, environmental, and safety aspects.

Project Deliverables

The project delivery will be through a written report and a presentation. The report should address the four main topics: introduction, development, conclusions, and bibliography, as described above. The report should include a detailed description of the chosen chemical reaction, the stoichiometry calculations performed, and a discussion of the practical implications of these calculations.

The presentation should include a visualization of the chemical reaction (with the help of specific software or applications if desired) and a clear explanation of the reaction, the stoichiometric calculations performed, and the conclusions drawn.

Students will be evaluated based on the clarity and accuracy of their report and presentation, as well as their ability to work as a team, manage their time effectively, and solve any problems that arise during the project.