Prepare a Salt by Titration Flashcards
All 6 cards in this deck
What are the steps to prepare a pure, dry salt from an acid and a soluble base?
e.g. sodium hydroxide solution and dilute hydrochloric acid- Pipette the alkali into a flask, add indicator and titrate with acid from a burette; record the volume needed.
- Repeat with the same volumes but no indicator.
- Evaporate part of the solution, leave to crystallise, then dry the crystals.
Why must a titration be used when a soluble reactant is used to make a salt?
Excess soluble reactant cannot be filtered off, so the acid and alkali must be mixed in exactly the right proportions.
Which apparatus is used to measure the acid and the alkali in a titration?
A burette for the acid and a (volumetric) pipette for the alkali.
Why is the titration repeated using the same volumes but without indicator?
So the indicator does not contaminate (colour) the salt crystals.
What colour change does phenolphthalein show at the end point when acid is added to an alkali?
From pink/magenta to colourless.
True or false? Universal indicator is the best indicator to use in a titration.
False. It changes through a range of colours, so there is no sharp end point; phenolphthalein or methyl orange is used.