How do you prepare a 250 cm³ of 0.1 M Na₂CO₃(aq) standard solution and use it for titration?

First, determine the molar mass of sodium carbonate ($\text{Na}_2\text{CO}_3$).

Next, calculate the moles of $\text{Na}_2\text{CO}_3$ required for 250 cm³ of 0.1 M solution.

Finally, calculate the mass of $\text{Na}_2\text{CO}_3$ needed.

1. Accurately weigh out 2.65 g of anhydrous sodium carbonate using a weighing boat and an electronic balance.
2. Transfer the weighed sodium carbonate into a beaker and dissolve it in a small amount (e.g., 50 cm³) of distilled water, stirring with a glass rod.
3. Carefully transfer the solution from the beaker into a 250 cm³ volumetric flask using a funnel.
4. Rinse the beaker and the funnel several times with small portions of distilled water, adding all washings to the volumetric flask to ensure complete transfer of the solute.
5. Add distilled water to the volumetric flask until the bottom of the meniscus is exactly on the 250 cm³ mark at eye level.
6. Stopper the volumetric flask and invert it several times to ensure the solution is thoroughly mixed and homogeneous.

B) Using the standard solution to determine the concentration of dilute sulphuric acid

1. Rinse a burette with dilute sulphuric acid and then fill it with the acid, ensuring no air bubbles are trapped. Record the initial burette reading.
2. Using a pipette, transfer exactly 25.0 cm³ of the prepared 0.1 M $\text{Na}_2\text{CO}_3$ standard solution into a clean conical flask.
3. Add 2-3 drops of phenolphthalein indicator to the sodium carbonate solution in the conical flask. The solution will turn pink.
4. Place the conical flask on a white tile under the burette. Slowly add the dilute sulphuric acid from the burette into the conical flask, swirling the flask constantly.
5. Continue adding the acid drop by drop until the pink color just disappears, indicating the endpoint of the titration.
6. Record the final burette reading and calculate the volume of acid used (titre).
7. Repeat the titration several times to obtain at least two concordant titres (volumes that are within $\pm 0.1 \text{ cm}^3$ of each other). Calculate the average of these concordant titres.

1. Write the balanced chemical equation for the reaction: $$\text{Na}_2\text{CO}_3(\text{aq}) + \text{H}_2\text{SO}_4(\text{aq}) \to \text{Na}_2\text{SO}_4(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$$ From the equation, the mole ratio of $\text{Na}_2\text{CO}_3 : \text{H}_2\text{SO}_4$ is 1:1.
2. Calculate the moles of $\text{Na}_2\text{CO}_3$ used in the titration: $$\text{Moles of Na}_2\text{CO}_3 = \text{Concentration of Na}_2\text{CO}_3 \times \text{Volume of Na}_2\text{CO}_3 \text{ (in dm}^3)$$ $$\text{Moles of Na}_2\text{CO}_3 = 0.1 \text{ mol/dm}^3 \times \frac{25.0}{1000} \text{ dm}^3$$
3. Using the 1:1 mole ratio from the balanced equation, the moles of $\text{H}_2\text{SO}_4$ reacted are equal to the moles of $\text{Na}_2\text{CO}_3$. $$\text{Moles of H}_2\text{SO}_4 = \text{Moles of Na}_2\text{CO}_3$$
4. Calculate the concentration of dilute sulphuric acid: $$\text{Concentration of H}_2\text{SO}_4 = \frac{\text{Moles of H}_2\text{SO}_4}{\text{Average volume of H}_2\text{SO}_4 \text{ (titre in dm}^3)}$$