4.2 - Acid-base titrations Flashcards
What is a titration?
A titration is a technique used to accurately measure the volume of one solution that reacts exactly with another solution.
This can be used for finding the concentration of a solution, identifying unknown chemicals and finding the purity of a substance.
Where is checking purity important?
Checking purity is an important aspect of quality control, especially for compound manufactured for human use such as medicines, food and cosmetics.
What is a standard solution?
A standard solution is a solution of known concentration.
A volumetric flask is used to make up a standard solution very accurately.
What is the typical tolerance for a 250cm3 volumetric flask?
+/- 0.30 cm3
What is the procedure for preparing a standard solution?
1) Solid is weighed accurately.
2) Solid is dissolved in beaker of distilled water, with less distilled water than is needed to fill the volumetric flask to the mark.
3) Solution transferred to a volumetric flask. The last traces of solution are rinsed into the flask with distilled water.
4) The flask is carefully filled to the graduation line, until the bottom of the meniscus lines up exactly with the mark.
5) Finally, the volumetric flask is inverted several times to mix the solution thoroughly.
What is the effect on the titre if, during preparation of the standard solution, the flask is filled with water above the graduation line?
The solution will be too dilute.
Titre is higher than it should be.
What is the effect on the titre if, during preparation of the standard solution, the flask is not inverted?
Titration results will be inconsistent, due to uneven distribution of solid in solution.
What is the uncertainty of a 50cm3 burette?
+/- 0.1 cm3
How are burette readings recorded?
A burette reading is recorded to the nearest half division.
Each burette reading is measured to the nearest +/-0.05cm3.
So the reading always has two decimal places.