Prepare a Salt by Titration Flashcards
All 6 cards in this deck
Why must a titration be used to make a soluble salt from an acid and a soluble reactant (alkali)?
Excess alkali cannot be filtered off, so the exact volumes needed must be found to mix them in the correct proportions.
What are the steps of an acid–alkali titration to find the volumes needed for a salt?
e.g. hydrochloric acid and sodium hydroxide solution
- Use a pipette to measure a fixed volume of the alkali into a conical flask and add a few drops of indicator.
- Add acid from a burette, swirling, until the indicator just changes colour.
- Record the volume of acid used (the titre).
After a titration, how is a pure, dry sample of the salt obtained?
Repeat using the same volumes without indicator, then evaporate/crystallise the solution.
Why is the titration repeated without indicator when making the salt?
The indicator would contaminate the salt crystals.
True or false? After a correctly done acid–alkali titration, the solution left in the flask contains only salt and water.
True. The acid and alkali have been mixed in exactly the right proportions, so neither is in excess.
Why is universal indicator not used in a titration?
Its colour changes gradually over the pH range, so the end point is not clear. An indicator with one sharp colour change, such as phenolphthalein or methyl orange, is used instead.