Dilution of a Stock Solution

Oct 13, 2025 by magicalceylontours.com 75 views

Introduction

Molarity is a fundamental concept in chemistry that describes the concentration of a solution in terms of the number of moles of solute per liter of solution. In this article, we will explore how to calculate the molarity of a diluted solution, specifically a 250 mL $H_2SO_4$ solution made from a 10.0 M stock solution.

Understanding Molarity

Molarity is defined as the number of moles of solute per liter of solution. It is calculated using the formula:

Molarity (M) = Number of moles of solute / Volume of solution (in liters)

For example, if we have a solution with 2 moles of solute in 1 liter of solution, the molarity would be 2 M.

Dilution of a Stock Solution

When a stock solution is diluted, the concentration of the solute decreases. In this case, we have a 10.0 M stock solution of $H_2SO_4$ that is diluted to make a 250 mL solution. To calculate the molarity of the diluted solution, we need to know the volume of the stock solution used and the volume of the diluted solution.

Calculating the Molarity of the Diluted Solution

To calculate the molarity of the diluted solution, we can use the following formula:

Molarity of diluted solution = (Number of moles of solute in stock solution) / (Volume of diluted solution in liters)

Since we know the molarity of the stock solution (10.0 M) and the volume of the stock solution used (20.0 mL), we can calculate the number of moles of solute in the stock solution:

Number of moles of solute = Molarity of stock solution x Volume of stock solution (in liters) = 10.0 M x (20.0 mL / 1000 mL/L) = 0.2 moles

Now, we can calculate the molarity of the diluted solution:

Molarity of diluted solution = Number of moles of solute / Volume of diluted solution (in liters) = 0.2 moles / (250 mL / 1000 mL/L) = 0.2 moles / 0.25 L = 0.8 M

Conclusion

In this article, we calculated the molarity of a 250 mL $H_2SO_4$ solution made from a 10.0 M stock solution. We used the formula for molarity and the concept of dilution to determine the concentration of the solute in the diluted solution. The molarity of the diluted solution was found to be 0.8 M.

Frequently Asked Questions

What is molarity? Molarity is a measure of the concentration of a solution in terms of the number of moles of solute per liter of solution.
How do I calculate the molarity of a diluted solution? To calculate the molarity of a diluted solution, you need to know the number of moles of solute in the stock solution and the volume of the diluted solution.
What is the difference between molarity and concentration? Molarity is a measure of concentration in terms of moles per liter, while concentration can be measured in terms of grams per liter or other units.

References

Chemistry: An Atoms First Approach, by Steven S. Zumdahl
General Chemistry: Principles and Modern Applications, by Linus Pauling

Introduction

Molarity is a fundamental concept in chemistry that can be confusing, especially when it comes to dilution and concentration. In this article, we will answer some of the most frequently asked questions about molarity, covering topics such as dilution, concentration, and calculation.

Q: What is molarity?

A: Molarity is a measure of the concentration of a solution in terms of the number of moles of solute per liter of solution. It is calculated using the formula:

Molarity (M) = Number of moles of solute / Volume of solution (in liters)

Q: How do I calculate the molarity of a diluted solution?

A: To calculate the molarity of a diluted solution, you need to know the number of moles of solute in the stock solution and the volume of the diluted solution. You can use the formula:

Molarity of diluted solution = (Number of moles of solute in stock solution) / (Volume of diluted solution in liters)

Q: What is the difference between molarity and concentration?

A: Molarity is a measure of concentration in terms of moles per liter, while concentration can be measured in terms of grams per liter or other units. For example, a solution with 2 moles of solute in 1 liter of solution has a molarity of 2 M, but it may have a concentration of 20 g/L if the solute has a molecular weight of 10 g/mol.

Q: How do I calculate the number of moles of solute in a solution?

A: To calculate the number of moles of solute in a solution, you need to know the molarity of the solution and the volume of the solution in liters. You can use the formula:

Number of moles of solute = Molarity of solution x Volume of solution (in liters)

Q: What is the relationship between molarity and volume?

A: Molarity is inversely proportional to volume. As the volume of a solution increases, the molarity decreases, and vice versa.

Q: How do I dilute a stock solution to a specific molarity?

A: To dilute a stock solution to a specific molarity, you need to know the molarity of the stock solution and the desired molarity of the diluted solution. You can use the formula:

Volume of stock solution = (Molarity of stock solution x Volume of diluted solution) / (Molarity of diluted solution)

Q: What are some common mistakes to avoid when calculating molarity?

A: Some common mistakes to avoid when calculating molarity include:

Not converting units correctly (e.g., mL to L)
Not using the correct formula for molarity
Not considering the dilution factor when calculating molarity
Not checking units for consistency

Q: How do I convert between molarity and other units of concentration?

A: To convert between molarity and other units of concentration, you need to know the molecular weight of the solute and the desired unit of concentration. You can use the following formulas:

Molarity (M) = Concentration (in g/L) / Molecular weight (in g/mol)
Concentration (in g/L) = Molarity (M) x Molecular weight (in g/mol)

Q: What are some real-world applications of molarity?

A: Molarity has many real-world applications, including:

Pharmaceutical industry: Molarity is used to calculate the concentration of active ingredients in medications.
Food industry: Molarity is used to calculate the concentration of ingredients in food products.
Environmental science: Molarity is used to calculate the concentration of pollutants in water and air.

Conclusion

Molarity is a fundamental concept in chemistry that can be confusing, especially when it comes to dilution and concentration. By understanding the basics of molarity and how to calculate it, you can apply this knowledge to a wide range of real-world applications.

Frequently Asked Questions

What is molarity?
How do I calculate the molarity of a diluted solution?
What is the difference between molarity and concentration?
How do I calculate the number of moles of solute in a solution?
What is the relationship between molarity and volume?
How do I dilute a stock solution to a specific molarity?
What are some common mistakes to avoid when calculating molarity?
How do I convert between molarity and other units of concentration?
What are some real-world applications of molarity?

References

Chemistry: An Atoms First Approach, by Steven S. Zumdahl
General Chemistry: Principles and Modern Applications, by Linus Pauling
Molarity and Concentration: A Guide to Understanding Chemical Solutions