Determining the Molarity of a Diluted H2SO4 Solution: A Comprehensive Guide

Dilution is a common operation in chemistry, where a concentrated solution is mixed with a solvent to achieve a desired concentration. This article provides a step-by-step guide to calculating the molarity of a solution when water is added to a concentrated acid. Specifically, let's explore the scenario where 500 ml of water is added to 300 ml of 0.4M H2SO4 solution. We'll walk through the calculation method and provide an in-depth understanding of the process.

Understanding Molarity and Dilution

Molarity (M) is a measure of the concentration of a solution, defined as the number of moles of solute per liter of solution. The general formula for calculating molarity is:

Molarity (M) Moles of solute / Volume of solution (L)

Dilution is the process of reducing the concentration of a solution by adding a solvent (water in this case) to it. The dilution principle states that the number of moles of solute remains constant, but the volume of the solution changes.

Calculating the Molarity of a Diluted Solution

Let's perform the calculations to determine the molarity of the resulting solution when 500 ml of water is added to 300 ml of 0.4M H2SO4 solution.

Step 1: Calculate the Moles of H2SO4 in the Original Solution

The first step is to find out how many moles of H2SO4 are present in the original 300 ml (0.300 L) of 0.4 M solution.

Moles of H2SO4 Molarity × Volume (in liters)

Moles of H2SO4 0.4 M × 0.300 L 0.12 moles

Step 2: Calculate the Total Volume of the Solution After Dilution

When 500 ml of water is added to the 300 ml of H2SO4 solution, the total volume of the diluted solution becomes:

Total volume 300 ml 500 ml 800 ml 0.800 L

Step 3: Calculate the Molarity of the Diluted Solution

Using the dilution formula, we can now calculate the molarity of the diluted solution:

Molarity Moles of solute / Total volume (in L)

Molarity 0.12 moles / 0.800 L 0.15 M

Therefore, the molarity of the resulting solution is 0.15 M H2SO4.

Further Considerations

This calculation assumes volume additivity, which is a reasonable approximation for dilute solutions. However, it's important to note that for highly concentrated solutions or when dealing with solvents with properties that significantly affect volume (like ethanol-water mixtures), volume additivity may not hold true.

Using the dilution equation:

V1 × C1 V2 × C2

Where:

V1 300 mL, C1 0.4 M, V2 800 mL, and we want to find C2.

300 mL × 0.4 M 800 mL × C2

C2 (300 × 0.4) / 800 0.15 M

This method gives us the same result, confirming our earlier calculation.

Practical Implications

The process of diluting H2SO4 is crucial in many chemical processes, from laboratory preparation to industrial applications. Understanding how to accurately calculate the molarity of the diluted solution ensures that reactions proceed under controlled and predictable conditions.

By mastering this concept, chemists and researchers can ensure the safety and efficiency of their experiments and processes. Always handle acids like H2SO4 with the appropriate safety precautions, as they can be highly corrosive and potentially hazardous.

Conclusion

In summary, the molarity of the resulting solution when 500 ml of water is added to 300 ml of 0.4M H2SO4 solution is 0.15 M. This example demonstrates the principles of solution concentration and dilution, providing a clear method for calculating molarity in such scenarios. Understanding these concepts is essential for any chemist or scientist working with solutions in laboratory settings.