Core practical 2 Flashcards
Prepare a standard solution from a solid acid and use it find the concentration of a solution of sodium hydroxide
what safety measures should you consider?
-wear goggles
-sulfamic acid can be toxic
-ensure when the burette is filled that the top of the burette is below eye level
what are steps 1-5 of the experiment?
- weigh an empty test tube and then scoop 2.5g of sulfamic acid into the test tube
- reweigh the test tube and its contents
- dissolve the sulfamic acid in 100cm cubed of water in a beaker
- transfer the solution into a 250cm cubed volumetric flask and make the solution up to the mark with deionised water
- prepare apparatus for the titration
what are steps 6-9 of the experiment?
- pour 25.0cm cubed of NaOH of an unknown concentration into the conical flask
- add 4 drops of methyl orange
- titrate the contents until you have two concordant titres
- record results in a table
A 250cm cubed flask has an accuracy of +/- 0.6cm^3. Calculate the percentage uncertainty.
0.6/250 = 0.24%
Why should the pipette be rinsed with sodium hydroxide solution after washing it with water?
water left in the pipette will dilute the sodium hydroxide, changing the number of moles used
Why is there no need to dry the conical flask after washing it out between trails?
the water will not change the number of moles of NaOH as this is measured before it is put into the flask
What is another indicator that could be used in this titration and state the colour change that would be seen at the end point.
Phenolphthalein
pink to colourless
