Volumetric Analysis Flashcards
(27 cards)
What are the steps to the filling of burette?
- Rinse burette with a small amount of the solution to be used (to ensure that water is flushed out).
- Fill the burette to the top with solution to be used, using a filter funnel. (Ensure the tap is closed first. If tap is tight, do not force it. Ask for help to loosen the tap).
- Release the solution by turning the tap. Ensure that there are no bubbles in the lower part of the burette, especially the part after the tap.
- Note that for the initial reading, the lower meniscus of the solution does not have to be at the 0.00cm cube mark.
Record the initial burette in a table. (Include details like titration number, final reading, initial reading, volume of Q used and best titration results)
- Leave the burette aside for any air bubbles in the solution to dissipate.
How should readings be read and recorded as for a burette?
Readings should be read from the top to the bottom.’
So let’s say there is a certain amount of solution in the burette and the meniscus touches the line 9.05, the initial reading would be 9.05 and not the total volume of the burette minus 9.05
Readings should be recorded to 2d.p.
What are the steps to pipetting solution into conical flask?
- Fix a pipette-filler to the pipette. (Note: push only about 1cm of the pipette into the pipette filler) [Caution: DO NOT hold the pipette bulb when fixing the pipette filler, the pipette. Might break!) you can instead, hold the top of the pipette and the red thing (pipette-filler)
- Rinse the pipette by drawing a small amount of the solution into the pipette and then discarding it. (This is to ensure that water used in the washing earlier is removed).
- Pump the solution up to slightly above the 25.0 cm cube (thin brown) line, then releasing the solution carefully so that the lower meniscus touches the 25.0 cm cube mark. [Caution: DO not allow the solution to enter the pipette filler]
- Check quickly that there are no air bubbles in the solution.
- Carefully transfer solution into a conical flask. (The flask should have been rinsed with distilled water. DO NOT rinse the flask with the solution to be filled.)
- Tilt the flask slightly and gently scratch or tap the pipette tip on a dry portion on the bottom of the flask. This ensures that the last drop of solution would leave the pipette. However, DO NOT blow out any of the solution.
What should you take note when fixing a pipette-filler to the pipette?
- Fix a pipette-filler to the pipette. (Note: push only about 1cm of the pipette into the pipette filler) [Caution: DO NOT hold the pipette bulb when fixing the pipette filler, the pipette. Might break!) you can instead, hold the top of the pipette and the red thing (pipette-filler)
Why do you need to rinse the pipette by drawing a small amount of the solution into the pipette and then discarding it?
This is to ensure that water used in the washing earlier is removed).
What should you take note when pumping the solution up to the pipette?
DO NOT allow the solution to enter the pipette filler.
What should you take note after pumping the solution up to the pipette?
Check quickly that there are no air bubbles in the solution.
What should you take note before carefully transferring the solution into a conical flask?
The flask should have been rinsed with distilled water. DO NOT rinse the flask with the solution to be filled.
Why do we need to tilt the flask slightly and gently scratch or tap the pipette tip on a dry portion on the bottom of the flask when pipetting solution into conical flask? What should you take note of?
This ensures that the last drop of solution would leave the pipette. However, DO NOT blow out any of the solution.
Will not rinsing a pipette or burette affect your measurements?
Yes.
If you don’t rinse with the solution (e.g., acid or alkali you’re using), leftover distilled water or another chemical inside the pipette or burette will:
Dilute the solution you’re measuring.
Cause the concentration to be lower than it should be.
This leads to inaccurate volume readings and incorrect titration results.
This ensures no contamination or dilution occurs that could change the result of your experiment.
Why rinse pipettes and burettes with the solution before using?
To prevent dilution of the solution by leftover distilled water.
If not rinsed properly, any water remaining inside can mix with the solution and reduce its concentration, leading to inaccurate results.
What does rinsing with a solution mean?
Rinsing means pouring a small volume of the solution into the equipment, swirling it around (or letting it run through for a burette), then discarding it.
You are not filling it up—just enough to coat the inside and flush out leftover water.
Which solution do I use for rinsing?
For the pipette: Rinse with the solution that will go into the conical flask (usually alkali or acid).
For the burette: Rinse with the solution that will go into the burette (usually the titrant).
Never rinse with water before use without following with the actual solution!
Why don’t we rinse the conical flask with solution?
Because the volume in the conical flask does not need to be exact — it’s the reaction container, not a measuring tool.
Rinsing it with the solution could cause some of the solution to remain inside, altering the amount you think you’ve added.
What is the rinsing sequence before use in titration?
Step 1: Rinse with Tap Water
Purpose: To remove any dust, chemicals, or residues from previous use.
How: Pour tap water in, swirl (or for a burette, run water through the tap), and discard.
🔹 Step 2: Rinse with Distilled Water
Purpose: To remove impurities from tap water and ensure no ions or chemicals remain.
How: Repeat the rinsing as above using distilled water. Discard the water afterward.
🔹 Step 3: Rinse with the Solution to be Used
For Pipette: Rinse with the solution you will use in the pipette (e.g., sodium hydroxide).
For Burette: Rinse with the solution you will fill the burette with (e.g., hydrochloric acid).
Purpose: To flush out any remaining distilled water and ensure no dilution of the actual solution.
How: Use a small amount of the solution, swirl or let it flow through (for burette), then discard it into waste, not back into the stock solution.
What is titration?
Titration is one of the methods of volumetric analysis, in which the unknown concentration of a solution can be determined by reacting it with another solution of known concentration. This is done by measuring the exact volumes of the two reagents needed for a complete reaction.
What is a standard solution? How is it prepared?
The solution of known concentration is called a standard solution. It is prepared by dissolving an accurate amount of solute in water using a volumetric flask of a specified volume.
To determine the concentration of a sulfuric acid solution, it is titrated with a standard solution of ________________ of __________.
of sodium hydroxide of 0.100 mol dm to the power of -3.
How should you draw the table to record the burette reading?
______________________________________________
Titration number | 1 | 2 |
Final reading/cm cube. | | |
Initial reading/cm cube. | | |
Volume of Q used/cm cube | | |
Best titration results ( tick) | | |
What are the titration steps?
Step 1: Washing Apparatus
Step 2: Filling of burette
Step 3: Pipetting solution into conical flask
Step 4: Scout titration
Step 5: Accurate titrations
For step 4, scout titration, what are the specific steps?
- Place a white tile below the conical flask to enable you to see the colour change more easily.
- Add two to three drops of the ph indicator.
- Carefully release the solution in the burette (called the titrant) into the conical flask rapidly, swirling the mixture in a circular motion and gently. You should try to ensure that every drop goes into the centre of the flask. In any case, should some of the drops remain on the sides of the conical flask, you may flush them into the mixture with some distilled water.
- Stop when the indicator in the solution just changes colour. This is known as the end-point of the titration. Keep this mixture for references.
- Record the final burette reading.
How do you record the volume of Q used/ cm cube based on the final reading/ cm cube and initial reading/cm cube?
Subtract the initial reading/cm cube from the final reading/cm cube.
For step 5, accurate titrations, what are the specific steps?
- Repeat the titration for the second flask. This time you add the titrant from the burette as you did (rapidly) for the first attempt, but stop about 1cm cube before the expected approximate volume (say 26.20 cm cube in this example).
- Now add the titrant dropwise, swirling as you add each drop, until upon adding one drop the indicator changes colour permanently.
- Repeat the titration until you get consistent readings within 0.10 cm cube of each other.
Recording of values.
- Tick the TWO best titration results.
Show WORKING for calculate of average (25.20 + 25.10) divide by 2.
using these results, the average volume of Q required was 25.15 cm cube.
Note that the average must be in 2 d.p.
What does the equivalence point of a titration mean?
The equivalent point of a titration occurs when the sulfuric acid is fully neutralised by the added sodium hydroxide, i.e. it indicates the complete reaction of the two reagents.
The term “equivalence point” means that the solutions have been mixed in exactly the right proportions according to the chemical equation and no reactant remains.
