Titration Flashcards
In a titration, it’s important to wash the inside of the titration flak with distilled or deionised water as you approach the end-point
(a) Suggest one reason why it’s important to wash the inside of the flask (1)
(b) washing with water decreases the concentration of the reagents in the titration flask.
Suggest why washing with water does not affect the titre value. (1)
In a titration, it’s important to wash the inside of the titration flak with distilled or deionised water as you approach the end-point
(a) Suggest one reason why it’s important to wash the inside of the flask
To make sure all the solutions from both the burette and pipette react with each other and are in the flask
(b) washing with water decreases the concentration of the reagents in the titration flask.
Suggest why washing with water does not affect the titre value.
Water doesn’t change the number of moles of either reactants
A chemist was asked to make a standard solution of sodium carbonate. The chemist dissolved an accurately known mass of sodium carbonate in a small amount of water in a conical flask. The chemist then poured the solution into a 250 cm3 graduated flask and made the solution up to to the mark.
Suggest one improvement to the chemists procedure
A chemist was asked to make a standard solution of sodium carbonate. The chemist dissolved an accurately known mass of sodium carbonate in a small amount of water in a conical flask. The chemist then poured the solution into a 250 cm3 graduated flask and made the solution up to to the mark.
Suggest one improvement to the chemists procedure
Mix contents and use deionised water
In a titration experiment, a good technique is essential for an accurate result to be obtained
(a) suggest a reason for removing the funnel after it has been used for filling the burette
(b) suggest one other source of error in using the burette to carry out a titration
(c) during the titration, the inside of the conical flask is rinsed with distilled water
Suggest why rinsing improves the accuracy of the titre
(d) explain why adding this extra water doesn’t change the volume of EDTA solution that is required in the titration
In a titration experiment, a good technique is essential for an accurate result to be obtained
(a) suggest a reason for removing the funnel after it has been used for filling the burette
As a droplet from the funnel could enter the burette affecting the volume, the reading and the titre
(b) suggest one other source of error in using the burette to carry out a titration
Air bubble in jet
(c) during the titration, the inside of the conical flask is rinsed with distilled water
Suggest why rinsing improves the accuracy of the titre
Ensures all reagents are able to react
(d) explain why adding this extra water doesn’t change the volume of EDTA solution that is required in the titration
The added water doesn’t affect the moles
The correct technique can improve the accuracy of a titration
(a) state why it’s important to fill the space below the tap in the burette with solution A before beginning an accurate titration
(b) suggest one reason why a 250 cm3 conical flask is preferred to a 250 cm3 beaker for a titration
(c) during a titration, a chemist rinsed the inside of the conical flask with deionised water. The water used for rinsing remained in the conical flask.
(i) give one reason why this rinsing can improve the accuracy of the end-point
(ii) explain why the water used for rinsing has no effect on the accuracy of the titre
(d) suggest one reason why repeating a titration makes the value of the average titre more reliable
The correct technique can improve the accuracy of a titration
(a) state why it’s important to fill the space below the tap in the burette with solution A before beginning an accurate titration
Space will fill during titration
(b) suggest one reason why a 250 cm3 conical flask is preferred to a 250 cm3 beaker for a titration
Less chance of losing liquid on swirling
(c) during a titration, a chemist rinsed the inside of the conical flask with deionised water. The water used for rinsing remained in the conical flask.
(i) give one reason why this rinsing can improve the accuracy of the end-point
Returns reagent on the sides of the flask to the reaction mixture to ensure that all of the acid / alkali reacts
(ii) explain why the water used for rinsing has no effect on the accuracy of the titre
This doesn’t change the number of moles of reagents
(d) suggest one reason why repeating a titration makes the value of the average titre more reliable
Idea that a single titration could be anomalous
A teacher noticed that a student had not cleared a large air bubble from below the burette tap in preparing the burette for use before starting the titration. This air bubble was ejected during the first titration of the volumetric flask mixture.
(a) State the effect that this mistake would have on the value of the titre
(b) state and explain the effect that this mistake would have on the average titre for this experiment
A teacher noticed that a student had not cleared a large air bubble from below the burette tap in preparing the burette for use before starting the titration. This air bubble was ejected during the first titration of the volumetric flask mixture.
(a) State the effect that this mistake would have on the value of the titre
The value of the titre would be higher than the true value
(b) state and explain the effect that this mistake would have on the average titre for this experiment
It should have no effect, the first titre can be ignored, subsequent titrations would be accurate
The maximum errors for the pipette and the burette are shown below. These errors take into account multiple measurements.
Pipette ± 0.05 cm3
Burette ± 0.15 cm3
Estimate the maximum percentage error in using each of these pieces of apparatus
Use an average titre 24.25 cm3 to calculate the percentage error in using the burette
Show your working.
Pipette =
Burette =
The maximum errors for the pipette and the burette are shown below. These errors take into account multiple measurements.
Pipette ± 0.05 cm3
Burette ± 0.15 cm3
Estimate the maximum percentage error in using each of these pieces of apparatus
Use an average titre 24.25 cm3 to calculate the percentage error in using the burette
Show your working.
Pipette = 0.05 x 100 / 25.0 = 0.2%
Burette = 0.15 x 100 / 24.25 cm3 = 0.6%
