Preparation of a 2.5 M Molar Sodium Carbonate (Na2CO3) and Sodium Chloride (NaCl) Solution: A Comprehensive Guide

Creating a precise concentration of a chemical solution requires careful calculation and measurement. This guide focuses on preparing a 500 mL solution of sodium carbonate (Na2CO3) and sodium chloride (NaCl) at 2.5 molar (M) concentrations using the principles of molarity. Understanding these steps can help achieve accurate and reliable solutions for a variety of applications in chemistry, biology, and other scientific fields.

Preparation of a 2.5 M Sodium Carbonate (Na2CO3) Solution

To prepare 500 mL of a 2.5 M solution of sodium carbonate (Na2CO3), follow these detailed steps:

Step 1: Calculate the Moles of Na2CO3 Needed

The first step involves calculating the number of moles of Na2CO3 required. The formula for molarity is:

Molarity (M) moles of solute / volume of solution (L)

Given that the desired concentration is 2.5 M and the volume of the solution is 500 mL (0.5 L), we can find the moles of Na2CO3:

Moles of Na2CO3 Molarity times; Volume of Solution

Moles of Na2CO3 2.5 M times; 0.5 L 1.25 moles

Step 2: Calculate the Mass of Na2CO3 Needed

Next, calculate the mass of Na2CO3 needed. The molar mass of Na2CO3 is approximately 106 g/mol. Use the following formula:

Mass of Na2CO3 moles of Na2CO3 times; molar mass of Na2CO3

Mass of Na2CO3 1.25 moles times; 106 g/mol 132.5 grams

Step 3: Weigh Out the Sodium Carbonate

Accurately weigh 132.5 grams of anhydrous sodium carbonate powder using a digital balance. This step is crucial for achieving the precise concentration required.

Step 4: Dissolve the Sodium Carbonate in Water

Transfer the sodium carbonate powder to a 500 mL volumetric flask. Add approximately 300 mL of distilled water to the flask. Stir thoroughly until the powder is completely dissolved. Once the powder is dissolved, add more distilled water until the volume reaches the 500 mL mark on the volumetric flask. Mix the solution by inverting the flask several times to ensure a homogeneous mixture.

Step 5: Verify the Concentration (Optional)

To ensure the accuracy of the solution, you can verify the concentration using titration or other analytical techniques.

Preparation of a 2.5 M Sodium Chloride (NaCl) Solution

Following a similar methodology, let's prepare 500 mL of a 2.5 M NaCl solution:

Step 1: Calculate the Amount of NaCl Needed

Determine the molarity and calculate the number of moles of NaCl required:

Moles of NaCl Molarity times; Volume in liters

Moles of NaCl 2.5 M times; 0.5 L 1.25 moles

Calculate the mass of NaCl needed. The molar mass of NaCl is approximately 58.44 g/mol:

Mass of NaCl moles of NaCl times; molar mass of NaCl

Mass of NaCl 1.25 moles times; 58.44 g/mol 73.05 grams

Step 2: Prepare the Solution

Use a balance to accurately weigh out 73.05 grams of NaCl. Dissolve the NaCl in a small volume of distilled water, typically around 200-300 mL, in a beaker. Carefully transfer the solution to a 500 mL volumetric flask. Add distilled water to the flask until the total volume reaches 500 mL. Stir well to ensure complete dissolution. Cap the flask and invert it gently several times to ensure thorough mixing.

Summary

By following these steps, you can prepare 500 mL of a 2.5 M NaCl solution using approximately 73.05 grams of NaCl. Precise measurements and proper technique are essential for achieving the desired concentration.

Safety Considerations

Both sodium carbonate (Na2CO3) and sodium chloride (NaCl) can cause skin and eye irritation. Always wear gloves and protective eyewear when handling these chemicals. Ensure proper ventilation in the laboratory environment.