Calculating the Concentration of Sodium Chloride from Sodium Carbonate Stoichiometry

Stoichiometry is a fundamental concept in chemistry that allows us to predict the amounts of reactants and products in a chemical reaction. When dealing with sodium carbonate and hydrochloric acid, mastering the calculation of the theoretical concentration of sodium chloride produced is crucial. This guide will walk you through the process, ensuring clarity and accuracy.

Step 1: Write the Balanced Chemical Equation

The reaction between sodium carbonate (Na2CO3) and hydrochloric acid (HCl) produces sodium chloride (NaCl), water (H2O), and carbon dioxide (CO2). The balanced chemical equation is:

Na2CO3(aq) 2HCl(aq) → 2NaCl(aq) H2O(l) CO2(g)

Step 2: Identify the Moles of Sodium Carbonate

To accurately calculate the moles of sodium chloride produced, you first need to determine the moles of sodium carbonate. This involves measuring the volume of the sodium carbonate solution and its concentration.

Volume of Sodium Carbonate Solution (V): Measure the volume of the sodium carbonate solution in liters (L).

Concentration of Sodium Carbonate Solution (C): Obtain the concentration of the sodium carbonate solution in moles per liter (mol/L).

Formula to calculate moles of sodium carbonate:

n C × V

Where:

n is the number of moles of sodium carbonate. C is the concentration of the sodium carbonate solution in mol/L. V is the volume of the sodium carbonate solution in liters (L).

Step 3: Determine Moles of Sodium Chloride Produced

From the balanced equation, 1 mole of sodium carbonate produces 2 moles of sodium chloride. Therefore, the moles of sodium chloride can be calculated as follows:

nNaCl 2 × nNa2CO3

Step 4: Calculate the Concentration of Sodium Chloride

If the total volume of the solution after the reaction is known, the concentration of sodium chloride can be calculated. Let's denote the total volume of the solution after the reaction as Vtotal (L).

Formula to calculate the concentration of sodium chloride:

CNaCl nNaCl / Vtotal

Where:

CNaCl is the concentration of sodium chloride in mol/L. nNaCl is the moles of sodium chloride produced. Vtotal is the total volume of the solution after the reaction in liters (L).

Example Calculation

Suppose you have 0.500 L of a 0.200 M sodium carbonate solution.

Calculate moles of sodium carbonate:

nNa2CO3 0.200 mol/L × 0.500 L 0.100 mol

Calculate moles of sodium chloride produced:

nNaCl 2 × 0.100 mol 0.200 mol

Calculate the concentration of sodium chloride, assuming the total volume after the reaction is 0.600 L:

CNaCl 0.200 mol / 0.600 L ≈ 0.333 mol/L

Conclusion

By following these steps, you can calculate the theoretical concentration of sodium chloride produced from a given volume and concentration of sodium carbonate. Always ensure to consider the total volume of the solution after the reaction when calculating the final concentration.