Practical skills assessment video - titration - standard solution

Summary

This video tutorial guides viewers through the process of preparing a 0.1 mol/dm³ sodium carbonate standard solution in a 250 cm³ volumetric flask. It covers the weighing by difference method to accurately measure 2.6 grams of anhydrous sodium carbonate, dissolving it in distilled water, and transferring the solution to the flask. The video emphasizes the importance of thorough rinsing, accurate volume measurement, and gentle mixing to ensure uniform concentration. It concludes with calculating the solution's molar concentration, resulting in a precise 0.0974 mol/dm³ solution.

Takeaways

• 🔍 To prepare a standard solution, you need to create a solution with a known concentration, specifically 0.1 mol/dm3 sodium carbonate in this case.
• 🔬 The process involves accurate measurement of the mass of sodium carbonate using a method called weighing by difference.
• 📏 A spatula is used to measure approximately 2.6 grams of anhydrous sodium carbonate, and the mass is recorded with the weighing boat.
• 🧪 The anhydrous sodium carbonate is then dissolved in distilled water in a 100 cm3 beaker until completely dissolved.
• 🧪 A 250 cm3 volumetric flask and a funnel are essential tools for transferring the solution into the flask.
• 💧 It's crucial to rinse the beaker and funnel with a wash bottle at least three times to ensure all the solution is transferred into the volumetric flask.
• 📏 The volumetric flask should be filled to the 250 cm3 mark with distilled water, observing the meniscus at eye level.
• 🔄 The flask must be gently inverted several times to ensure the concentration of sodium carbonate is uniform throughout the solution.
• 🏷️ The flask should be clearly labeled with the exact concentration of the solution.
• 🧮 The concentration of the standard solution is calculated by dividing the mass of anhydrous sodium carbonate by its molar mass and then by the volume in dm3.

Q & A

What is the purpose of making a standard solution in titration?

A standard solution is required in titration to have a solution of a known concentration, which is essential for accurately determining the concentration of the unknown solution being tested.

What is the concentration of the sodium carbonate solution being prepared in the script?

The concentration of the sodium carbonate solution being prepared is approximately 0.1 mol/dm³.

Why is a 250 cm³ volumetric flask used in this process?

A 250 cm³ volumetric flask is used to ensure the solution is prepared to a precise volume, which is necessary for accurate concentration calculations.

What method is suggested for accurately determining the mass of sodium carbonate?

The method suggested for accurately determining the mass of sodium carbonate is 'weighing by difference'.

How much anhydrous sodium carbonate is initially measured out using a spatula?

Approximately 2.6 grams of anhydrous sodium carbonate is measured out using a spatula.

What is the purpose of dissolving the sodium carbonate in distilled water?

Dissolving the sodium carbonate in distilled water ensures that the solute is completely dissolved, creating a homogeneous solution that can be accurately measured and used in titration.

Why is it important to rinse the beaker and funnel with a wash bottle during the transfer to the volumetric flask?

Rinsing the beaker and funnel with a wash bottle ensures that all of the sodium carbonate solution is transferred to the volumetric flask, preventing loss of solute and ensuring the concentration remains accurate.

How should distilled water be added to the volumetric flask during the preparation?

Distilled water should be added to the volumetric flask up to the 250 cm³ mark, with care taken to observe the meniscus at eye level to ensure accuracy.

What is the purpose of inverting the flask gently after adding water to the mark?

Inverting the flask gently after adding water to the mark ensures thorough mixing and uniform concentration of the sodium carbonate throughout the solution.

Why is it necessary to label the flask with the exact concentration of the solution?

Labeling the flask with the exact concentration of the solution is crucial for traceability and to ensure that the solution can be used correctly in subsequent experiments or analyses.

How is the molar mass of anhydrous sodium carbonate used in the calculation of the solution's concentration?

The molar mass of anhydrous sodium carbonate is used to calculate the amount of substance used by dividing the mass of the anhydrous sodium carbonate by its molar mass, which then allows for the calculation of the solution's concentration.

What is the final calculated concentration of the sodium carbonate solution as per the script?

The final calculated concentration of the sodium carbonate solution is 0.0974 mol/dm³.