RP1- b- Acid-base Titration Flashcards
What equipment is needed for titration?
Burette, pipette, pipette filler, conical flask, beaker, clamp stand, white tile, funnel, labelled beaker of HCl, Labelled beaker of sodium hydroxide, wash bottle
Describe the method for a simple Acid-base Titration.
- Wash all glassware with water
- Wash pipette with NaOH solution
- Rinse burette with Acid and secrue to clamp stand
- Use the pipette with the pipette filler to accurately measure out 25cm^3 of the NaOH solution and place into a conical flask. Carefully touch the end of the pipette against the side of the flask and get the final drop of solution out of the pipette.
- Add 3 drops of Indicator -Phenolphthalein) to the conical flask
- Using a funnel, carefully fill the burette with acid a little over the 0cm3 line.
- Gently rinse out some of the acid into a waste beaker until the miniscus is on the 0cm3 line
- Remove the funnel
- Record the start volume in a table to 2 D.p
- Place a white tile on the clamp stand and place the conical flask full of NaOH on top of it under the burette
- Add acid to the conical flask. Continually swirl the flask to ensure through mixing. When 20cm^3 of acid has been added, carry on adding the acid slowly, until the solution turns from colourless to pink
- Record volume of acid to 2d.p and calculate the volume of acid added. This is the rough titration
- Repeat experiment 3/4 times to gain accurate results
- the end point is when solution turns from colourless to pink.
Why is it important to remove excess acid from the burette?
-If the jet space/Airlock is not filled it will lead to errors
-if it then fills during the titration, leading to a larger than expected titre reading.
Why is a conical flask preferred?
A conical flask is used in preference to a beaker because it is easier to swirl the mixture in a conical flask without spilling the contents.
Why do we remove the funnel after it has been used for filling the burette?
Any droplets from funnel may enter the burette
Why do we need to control the amount of universal indicator?
Only a few drops of indicator is require. If too much is added it will affect the titration result
- Because it is acidic
Why can we add water to the reaction mixture?
Distilled water can be used during a titration to wash the sides of the flask so that all reactants are washed into the mixture. This water does not affect the titration as it doesn’t change the number of moles of each reactant (acid + alkali)
why can rinsing improve the accuracy of the end-point of titration?
Returns reagent on side of the flask to the reaction mixture
Suggest one error in using the burette to carry out a titration?
Air bubble in the nozzel
What are concordant values?
lf 2 or 3 values are within 0.10cm3 and are therefore concordant, then the results are accurate and reproducible and the titration technique is good or consistent.
What are the maximum uncertainties for pipette and burette?
pipette = ±0.05 cm3
Burette = +0.15 cm3
What is uncertainty of a piece of equipment?
Is half the smallest scale reading
How do we reduce the uncertainty of the burette?
● To reduce the uncertainty in a burette reading the titre volume needs to be made larger. This could be done by: increasing the volume and concentration of the substance in the conical flask or by decreasing the concentration of the substance in the burette.
Why is rinsing the burette only with water before use an error?
This will reduce the concentration of the acid in the burette and lead to an inaccurate larger tire value
Why is having air trapped in the nozzle of the burette an error?
-can lead to greater inaccurate titre volume if the trapped air is released during a titration
