Preparation of Salts. Flashcards
What are the four ways of making salts?
- Reacting a metal with an acid.
- Reacting an insoluble base with an acid.
- Neutralising an alkali with an acid by the titration method.
- By precipitation.
How do you make a salt from an insoluble base (3)?
- add excess base to the acid.
- filter to remove any unreacted base that’s been added.
- heat the solution to evaporate the water, allowing crystals of the salt to form.
How do you make a salt from an soluble base (titration is the making of a soluble salt from a soluble base and acid) (7)?
- Measure the alkali into the titration flask using a volumetric pipette.
- Add a few drops of indicator solution to the alkali in the flask.
- Fill a clean burette with acid.
- Record the burette reading.
- Open the burette tap and let the acid flow into the flask.
- Keep adding acid slowly until the indicator changes color.
- Record the reading on the burette.
How do we make a salt from metals (6)?
- Add the metal to the acid in the flask so that the metal is in excess.
- Warm the flask gently to complete the reaction.
- Filter off the excess metal.
- Put the filtrate into an evaporating basin and evaporate the water until the crystalisation point is reached.
- Filter off the crystals and wash them with distilled water.
- Dry the crystals between sheets of filter paper.
What is a titration?
A titration is used to make a soluble salt from an acid.
To conduct a titration both acid and alkali must be soluble.
What are the salts made by the titration method included in?
Salts made by the titration method include salts of Group 1 elements and ammonium salts.
What is a precipitate?
The solid obtained when solutions of two soluble compounds are mixed is called a precipitate.
What are the 7 soluble compounds?
All salts of Group 1 elements.
All nitrates.
All ammonium salts.
Most chlorides, bromides and iodides (halides).
Most sulfates.
Group I hydroxide and carbonates are soluble.
Group I and II oxides react with water.
What are the 4 insoluble compounds (precipitation)?
Chlorides, bromides and iodides of silver and lead.
Sulfates of calcium, barium and lead.
Most hydroxide and carbonates.
Most metal oxides.
How do we make an insoluble salt (precipitation)?
making insoluble salts:
- mix the two solutions that will form the salt.
- filter to remove the solid insoluble salt.
- wash salt with distilled water.
- leave salt to dry on filter paper.
What are spectator ions?
The ions that do not take part in the reaction are called spectator ions.
Decribe the test for ammonia.
- Turns damp red litmus paper blue.
Describe the test for carbon dioxide.
- Bubble the gas through the limewater and it will turn milky (cloudy)
Describe the test for chlorine gas?
- When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.
Describe the test for hydrogen gas.
Use a burning splint held at the open end of a test tube of the gas.
▪ Creates a ‘squeaky pop’ sound.
