Contextualization

Molality is a property of chemical solutions that describes the quantity of particles present in the solution. This quantity is expressed in moles of solute per kg of solvent, being a fundamental chemical quantity to understand how substances interact with each other when dissolved in a liquid.

Molality is widely used in different fields of chemistry. For example, it is used to calculate the boiling and freezing points of solutions, understand osmotic pressure in biological systems and in the food industry, in the formulation of medications, and in the quality control of products.

In the real world, molality is an essential part of everyday and industrial chemistry. It allows chemists and engineers to control the concentration of solutions, which is essential for creating products with precision and quality. This is because molality is a concentration measure that does not change with temperature, unlike molarity. For example, in a juice factory, molality could be used to verify the exact amount of sugar added to the juice, ensuring that each batch of juice has the same flavor.

For these reasons, it is very important that as chemistry students, you understand the importance of molality, learn how to calculate it, and know how to use this concept to solve real-world problems.

Atividade Prática: The Magic of Molality

Project Objective

The objective of this project is to understand the concept of molality and calculate the molality of a practical solution that will be prepared by the students. The project will be carried out by groups of 3 to 5 students. The workload for each student is 2 to 4 hours and the deadline is one week.

Project Description

The students will prepare a sugar solution in water, measure the mass of the solute (sugar) and the solvent (water), and calculate the molality of the solution. This simple but effective activity will help students understand how molality is calculated in practice.

Necessary Materials

To carry out this activity, students will need the following:

• Precision scale.
• Weighing container.
• Sugar.
• Water.
• Measuring spoon.
• Glass jar with lid.
• Notebook for notes.

Step by Step

1. Weigh 100g of sugar in the weighing container using the precision scale and write down the mass in the notebook of notes.
2. Weigh 500g of water in the weighing container using the precision scale and write down the mass in the notebook of notes.
3. Add the sugar to the water in the glass jar and stir until the sugar is completely dissolved.
4. Calculate the molality of the solution using the formula: molality (m) = number of moles of solute / mass of the solvent (kg). (Note: the molar mass of sugar (sucrose) is approximately 342 g/mol).

Project Delivery

Groups must present a report containing the following topics:

1. Introduction: Provide context on the theme, relevance, and real-world application as well as the objective of this project.
2. Development: Explain the theory behind molality, detail the activity, indicate the methodology used, and finally present and discuss the results obtained.
3. Conclusion: Conclude the work by summarizing its main points, explaining the learnings obtained, and drawing conclusions about the project.
4. Bibliography: Indicate all sources on which they relied to work on the project such as books, web pages, videos, etc.

In addition, groups must attach the notes taken during the practical activity, including calculations and observations.