Titration test Flashcards
(34 cards)
Titration
An analytical technique used to determine the concentration of a solution using stoichiometry.
Raw data
Data obtained from experiment
Processed data
data found from calculations
IV
Volume of titrant added from the burette
DV
Colour change of the solution (shows the end point)
Control variable
-volume of analyte used/ solution being titrated
-Type of indicator
-Temperature and environment
- Same clean apparatus in each trial
Stand
Provides stable support for the titration setup; holds the boss head and clamp, which in turn hold the burette.
Boss head
A metal fitting that connects the clamp to the stand and allows height and position adjustments.
clamp
A metal device that firmly holds the burette in place, keeping it vertical and steady during the titration to ensure accurate volume readings.
burette
A long glass tube marked with volume graduations, used to dispense the titrant (solution of known concentration) precisely into the analyte.
funnel
Sometimes used to transfer the analyte into the flask from a beaker, ensuring all the sample is included. Lift slightly to avoid spluttering of solution
erlenmeyer flask
Contains the analyte (solution of unknown concentration). Its narrow neck allows easy swirling without splashing.
method
- Solution with unknown concentration is added to the cup and transferred to erlenmeyer in a fixed volume using a pipette and bulb filler (glass to glass, 45 degree angle, use finger to not tap)
- Add a few drops of universal indicator
- Clamp a burette with a boss attached to the stand and fill it with solution of known concentration between 1 and 5 ml
- Place a white tile or white surface onto the base of the stand to visualize colour changes of the indicator in the erlenmeyer in a clear way during the titration
- Record the initial volume of solution in the burette to two decimal places at an eye level to avoid parallax error
- Perform the titration and run at least three trials to obtain an average and calculate the concentration with accuracy
uncertainty in titrated volume
end point + start point.
0.05 +0.05 = 0.10
mol of unknown- using ratio
mol unknown=mol known×(coefficient of known / coefficient of unknown)
reasons calculated concentration is above literature value
Overshooting the Endpoint
– Too much titrant was added after the neutralisation point. The analyte may have turned blue or another basic colour, meaning more volume was recorded than actually needed.
Incorrect Starting Volume
– If the initial burette reading was too high, it would appear that more titrant was added than actually was, leading to an overestimation.
Air Bubbles or Leaks
– Air bubbles in the burette nozzle or a slowly dripping tap could result in extra titrant being delivered, which would not be accurately measured.
Not Swirling Properly
– Incomplete mixing during titration can cause a delayed or uneven colour change. This may lead you to add more titrant than necessary, increasing the calculated concentration.
reasons calculated concentration is below literature value
Used Less Analyte Than Expected
– If the analyte solution was spilled or splashed before the titration, the amount of substance being neutralised was reduced, so less titrant would be needed, lowering the calculated concentration.
Leaking Burette
– If the burette leaked during titration, more titrant may have been added than recorded, meaning the result underestimates how much base was truly used.
Endpoint Judged Too Early
– If the titration was stopped before full neutralisation, the recorded volume would be too low, and the analyte’s calculated concentration would be lower than the actual value.
Dilution of the Analyte (Acid or Base)
– If the analyte was accidentally diluted before pipetting, for example by using a wet beaker or pipette, the number of moles in the measured volume would be lower, resulting in a calculated concentration that is too low.
Adding Distilled Water During the Titration
Although distilled water was added to the Erlenmeyer flask to rinse down the sides and ensure all analyte was mixed in, this does not affect the concentration calculation. This is because the number of moles of analyte remains the same, and titration is based on mole ratios, not solution concentration in the flask. However, if the analyte was accidentally diluted before pipetting (e.g. from a wet cup or pipette), then fewer moles would be present in the measured volume. This would lead to a calculated concentration lower than the literature value.
Percentage error
Used to express the difference between experimental results and accepted value
% error= /experimental result- accepted value/
/ accepted value x100%
Conclusion:
State the magnitude number (x%)
Direction of percentage error (my results were x% higher or lower than the literature value)
evaluation answer
The percentage error shows that my calculated concentration was 8.5% lower than the expected (literature) value. This suggests that while the result is reasonably close, there may have been small procedural or measurement errors that caused underestimation. Possible causes include stopping the titration too early (before full neutralisation), some acid spilling, or the analyte being accidentally diluted before pipetting. Although the error is under 10%, improving the technique (such as adding the titrant more slowly near the endpoint and using a sharper indicator) could help reduce this error and increase the accuracy of the result.
table
trial, start point, end point, observations, titration volume, NaOH mmols, H2SO4 mmols, concentration of H2SO4
make sure to add the measure of uncertainty
pipette
measures and transfers a fixed, accurate volume of the analyte.
bulb filler
safely suctions the solution into the pipette against gravity.
