Practical skills assessment video - titration - standard solution
Summary
TLDRThis 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.
Outlines
🧪 Preparing a Standard Solution
This paragraph outlines the process of preparing a standard solution of sodium carbonate with a known concentration of 0.1 mol/dm3. The process begins with accurately measuring the mass of anhydrous sodium carbonate using a method called weighing by difference. Approximately 2.6 grams of the compound is measured and then transferred to a 100 cm3 beaker. After dissolving the sodium carbonate in distilled water, the solution is transferred to a 250 cm3 volumetric flask using a funnel and glass rod. The beaker and funnel are rinsed with distilled water to ensure all of the solution is transferred. The volumetric flask is then filled to the 250 cm3 mark with distilled water, and the solution is mixed by inverting the flask. The concentration of the solution is calculated by dividing the mass of sodium carbonate by its molar mass and the volume of the solution in dm3, resulting in a concentration of 0.0974 mol/dm3.
Mindmap
Keywords
💡Titration
💡Standard Solution
💡Molar Concentration
💡Anhydrous Sodium Carbonate
💡Weighing by Difference
💡Volumetric Flask
💡Meniscus
💡Molar Mass
💡Distilled Water
💡Rinse
💡Labeling
Highlights
Introduction to creating a standard solution with a known concentration.
Preparation of a 0.1 mol/dm3 sodium carbonate solution in a 250 cm3 volumetric flask.
Emphasis on the importance of accurate measurements and calculations for precise concentration.
Method of weighing by difference to determine the exact mass of sodium carbonate.
Use of a spatula to measure approximately 2.6 grams of anhydrous sodium carbonate.
Recording the mass of sodium carbonate with the weighing boat.
Transfer of the solid to a 100 cm3 beaker and re-weighing the boat for mass calculation.
Dissolving the anhydrous sodium carbonate in distilled water and stirring until completely dissolved.
Utilization of a 250 cm3 volumetric flask and a funnel for solution transfer.
Technique of pouring the solution down a glass rod into the flask for smooth drainage.
Rinsing the beaker with a wash bottle and transferring the rinse to the volumetric flask.
Careful addition of distilled water up to the 250 cm3 mark without exceeding it.
Observing the meniscus at eye level for accurate volume measurement.
Inversion of the flask to ensure uniform concentration of sodium carbonate.
Clear labeling of the flask with the exact concentration of the solution.
Calculation of the molar mass of anhydrous sodium carbonate.
Determination of the amount of substance used by dividing mass by molar mass.
Conversion of volume units from cm3 to dm3 for concentration calculation.
Final known accurate concentration of the sodium carbonate solution is 0.0974 mol/dm3.
Transcripts
Before you carry out your titration you'll need to make up a standard solution,
that's the solution of a known concentration.
In this case we'll be
making up a solution that's about 0.1 mol/dm3 sodium carbonate
in a 250 cm3 volumetric flask.
In this video we'll run through the steps required to make up your standard solution,
including all of the measurements and calculations you'll need
to carry out to get the exact concentration of your sodium carbonate solution.
To make up the standard solution, it's necessary to know accurately the exact
mass of sodium carbonate, which will be dissolved in a known volume of water.
The best way to do that is by a method called weighing by difference.
Using a spatula, measure out approximately 2.6 grams of anhydrous sodium carbonate.
Record the mass of the sodium carbonate with the weighing boat.
Transfer this solid to 100 cm3 cubed beaker.
Re-weigh and record the mass of the used boat.
Using these measurements, you can calculate the exact mass of anhydrous sodium carbonate.
Next, take this anhydrous sodium carbonate
and dissolve in distilled water from a wash bottle.
Stir this solution thoroughly until the solid is completely dissolved.
For the next step, you'll need a 250 cm3 volumetric flask,
and a funnel.
Pour your solution down a glass rod and
through the funnel into the flask.
Make sure to raise the funnel, so that it drains smoothly.
To make sure all of your sodium carbonate solution is transferred
to the volumetric flask, you should use a wash bottle to rinse the beaker.
Make sure to add this rinse to the volumetric flask each time,
and do this at least three times.
Take care as well to only use a small amount of water,
so as to not go higher than the 250 cm3 mark
on the volumetric flask.
The same should also be done with the funnel.
Add distilled water to the 250 cm3 mark.
Take care to observe the meniscus at eye level,
rather than from above or below.
To make sure the concentration of anhydrous sodium carbonate is the same
throughout your solution, stopper the flask
and gently invert it several times.
Finally, you will need to label the flask clearly
including the exact concentration of your solution.
To calculate the concentration of your standard solution,
you first have to work out the molar mass of anhydrous sodium carbonate
as shown here.
To calculate the amount of substance used, you will then have to divide the
mass of the anhydrous sodium carbonate used by its molar mass.
As we know the volume of the solution in the volumetric flask is
250 cm3, we can calculate the concentration.
Remember to divide by a thousand to convert the units of volume
from cm3 into dm3.
So, the known accurate concentration of your sodium carbonate solution is
therefore 0.0974 mol/dm3.
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