5.3 - Salts Flashcards
How do we make soluble salts?
We make soluble salts by neutralising acids and crystallising the resulting solution.
Acid(aq) + Base(s)/Alkali(aq) → Salt(aq) + Water(l)
What is the insoluble base method?
This is the more common of the two ways of making a salt solution.
We do this when making salts that do not contain Na+, K+ or NH4+ ions.
Method for making salts with insoluble base method?
- Heat the acid. (hot acid has more energy so it reacts faster with the base)
- While stirring, add base until no more will dissolve. (this guarantees the base is in excess so that we know all the acid has been used up)
- Filter out the excess base
What is the less common way of making a salt solution?
the titration method
Method for making salts with titration method?
- Perform a titration to measure the volumes of acid and alkali that neutralise each other.
- Repeat the titration, but this time:
a. Don’t put the indicator in.
b. Use the burette to add exactly the right volume for neutralisation.
What do we do once we have a salt solution?
perform crystallisation.
What is the method of crystallisation?
- Heat the salt solution until crystals just start forming. (this causes the solution to become saturated)
- Allow the solution to cool in anevaporating basin for a few days
- Filter out the crystals.
- Dry the crystals by dabbing them with filter paper.
How can we make insoluble salts?
We make insoluble salts by mixing solutions to make a precipitate.
What is a precipitate?
A precipitate (ppt) is an insoluble solid that forms inside a solution.
Method for making insoluble salts via precipitation?
- Filter out the salt precipitate. (the residue is the salt we want to keep. The filtrate is the leftover solution)
- Rinse the salt with water. (this washes off traces of the leftover solution. It doesn’t dissolve our salt because it’s insoluble)
- Dry the salt by dabbing it with filter paper. (this removes the last few traces of water, leaving us with a pure dry salt)
