Calculating Mass of Water in Kilograms

Oct 13, 2025 by wbrum.org 133 views

Introduction

Molality is a crucial concept in chemistry that measures the concentration of a solution in terms of the number of moles of solute per kilogram of solvent. In this article, we will calculate the molality of a sodium chloride solution used for intravenous injection. The solution contains 0.86 g of NaCl in 100 g of water.

Understanding Molality

Molality is defined as the number of moles of solute per kilogram of solvent. It is denoted by the symbol 'm' and is calculated using the following formula:

m = moles of solute / mass of solvent (in kg)

To calculate the molality of the solution, we need to determine the number of moles of NaCl and the mass of water in kilograms.

Calculating Moles of NaCl

The molar mass of NaCl is 58.44 g/mol. To calculate the number of moles of NaCl, we can use the following formula:

moles of NaCl = mass of NaCl / molar mass of NaCl

Substituting the given values, we get:

moles of NaCl = 0.86 g / 58.44 g/mol = 0.0147 mol

Calculating Mass of Water in Kilograms

The mass of water is given as 100 g. To convert this to kilograms, we can divide by 1000:

mass of water (in kg) = 100 g / 1000 = 0.1 kg

Calculating Molality

Now that we have the number of moles of NaCl and the mass of water in kilograms, we can calculate the molality using the formula:

m = moles of NaCl / mass of water (in kg)

Substituting the values, we get:

m = 0.0147 mol / 0.1 kg = 0.147 m

Discussion

The calculated molality of the solution is 0.147 m. This means that the solution contains 0.147 moles of NaCl per kilogram of water. This value is an important parameter in the preparation of intravenous solutions, as it affects the concentration of the solution and the rate at which the solute is absorbed by the body.

Conclusion

In conclusion, we have calculated the molality of a sodium chloride solution used for intravenous injection. The solution contains 0.86 g of NaCl in 100 g of water, and the calculated molality is 0.147 m. This value is an important parameter in the preparation of intravenous solutions, and it is essential to ensure that the solution is prepared correctly to avoid any adverse effects.

References

CRC Handbook of Chemistry and Physics, 97th Edition
International Conference on Harmonization (ICH) Guidelines for the Preparation of Intravenous Solutions

Additional Information

The molality of a solution can be affected by various factors, including temperature and the presence of other solutes.
The concentration of a solution can be expressed in terms of molality, molarity, or mass percentage.
The preparation of intravenous solutions requires careful attention to detail to ensure that the solution is prepared correctly and safely.
Frequently Asked Questions (FAQs) about Molality and Intravenous Solutions ====================================================================================

Q: What is molality, and why is it important in the preparation of intravenous solutions?

A: Molality is a measure of the concentration of a solution in terms of the number of moles of solute per kilogram of solvent. It is an important parameter in the preparation of intravenous solutions because it affects the concentration of the solution and the rate at which the solute is absorbed by the body.

Q: How do I calculate the molality of a solution?

A: To calculate the molality of a solution, you need to determine the number of moles of solute and the mass of solvent in kilograms. You can use the following formula:

m = moles of solute / mass of solvent (in kg)

Q: What is the difference between molality and molarity?

A: Molality and molarity are both measures of concentration, but they differ in the units used. Molality is expressed in terms of moles of solute per kilogram of solvent, while molarity is expressed in terms of moles of solute per liter of solution.

Q: Why is it important to use the correct concentration of a solution for intravenous injection?

A: The concentration of a solution can affect the rate at which the solute is absorbed by the body. If the concentration is too high, it can cause adverse effects, while if it is too low, it may not be effective. Therefore, it is essential to use the correct concentration of a solution for intravenous injection.

Q: Can I use a solution with a high molality for intravenous injection?

A: No, it is not recommended to use a solution with a high molality for intravenous injection. A high molality can cause the solution to be too concentrated, which can lead to adverse effects.

Q: How do I prepare an intravenous solution with the correct concentration?

A: To prepare an intravenous solution with the correct concentration, you need to follow a standard procedure that involves measuring the amount of solute and solvent accurately. You should also use a calibrated pipette or burette to measure the volume of the solution.

Q: What are some common mistakes to avoid when preparing intravenous solutions?

A: Some common mistakes to avoid when preparing intravenous solutions include:

Using the wrong concentration of the solution
Not measuring the amount of solute and solvent accurately
Not using a calibrated pipette or burette to measure the volume of the solution
Not following a standard procedure for preparing the solution

Q: What should I do if I make a mistake when preparing an intravenous solution?

A: If you make a mistake when preparing an intravenous solution, you should immediately stop the preparation process and discard the solution. You should then follow the standard procedure for preparing the solution again, and verify that the solution has the correct concentration.

Q: Can I use a solution that has been prepared by someone else for intravenous injection?

A: No, it is not recommended to use a solution that has been prepared by someone else for intravenous injection. You should always verify that the solution has been prepared correctly and has the correct concentration before using it for intravenous injection.

Q: What are some resources that I can use to learn more about molality and intravenous solutions?

A: Some resources that you can use to learn more about molality and intravenous solutions include:

The CRC Handbook of Chemistry and Physics
The International Conference on Harmonization (ICH) Guidelines for the Preparation of Intravenous Solutions
Online tutorials and courses on pharmacology and pharmacy practice
Professional organizations and associations related to pharmacy and pharmacology.