Calculating the Concentration of NaCl After Mixing Solutions

Introduction

Understanding how to calculate the concentration of a solute after mixing different solutions is a fundamental concept in chemistry. In this article, we will delve into the process of determining the new concentration of NaCl (sodium chloride) after mixing two solutions of NaCl with different molarities. This topic is particularly relevant for students and professionals in chemistry, biochemistry, and related fields. We’ll explain the step-by-step process and provide an example to illustrate the calculation.

Concepts and Principles

Before we dive into the specific problem, let's review the key concepts involved:

Molarity (M)

Molarity is defined as the number of moles of a solute per liter of solution. It is a standard unit for expressing the concentration of a solution and is denoted by M.

Dilution

Dilution refers to the process of increasing the volume of a solution without changing the amount of the solute. This is often achieved by adding more solvent to the solution, but in this case, we are dealing with mixing different solutions to achieve a new concentration.

Example Problem: Concentration of NaCl After Mixing Solutions

Let's consider the scenario where we have two NaCl solutions and we want to find the concentration of the resulting solution after they are mixed. The specific details are as follows:

10 mL of 0.05 M NaCl 20 mL of 0.1 M NaCl

Step 1: Calculate Millimoles of NaCl in Each Solution

First, we need to determine the millimoles of NaCl in each solution. Millimoles are simply milliliters multiplied by molarity.

For the first solution: 10 mL × 0.05 M 0.5 millimoles

For the second solution:

20 mL × 0.1 M 2 millimoles

The total millimoles of NaCl in the combined solution is the sum of the millimoles from both solutions:

0.5 millimoles 2 millimoles 2.5 millimoles

Step 2: Calculate the Total Volume of the Combined Solution

Next, we need to calculate the total volume of the combined solution. This is done by adding the volumes of the two solutions.

10 mL 20 mL 30 mL

Step 3: Determine the New Concentration

Finally, we use the total millimoles and the total volume to determine the new concentration in molarity (M). Millimoles per milliliter (mmol/mL) can be converted directly to molarity (M) since 1 M is equivalent to 1000 mmol/L.

M new 2.5 30 0.0833 M

The new concentration of the mixed NaCl solution is 0.0833 M.

Conclusion

Understanding and applying the concepts of molarity and dilution is crucial in chemistry. By following the steps outlined in this article, you can easily determine the concentration of a solute after mixing different solutions. This skill is not only beneficial in laboratory settings but also in a wide range of applications, from pharmaceuticals to environmental science.

Further Reading and Resources

For those interested in diving deeper into this topic, here are some additional resources and further reading materials:

Examples of Molarity Calculation Dilution Calculations Detailed Guide to Solutions and Concentrations