C4 Flashcards
pls dont fail DAWG (40 cards)
Reaction between acid and base
acid + base → salt + water
Reaction between acid and metal
acid + metal → salt + hydrogen gas
Reaction between acid and metal carbonate
acid + metal carbonate → salt + water + carbon dioxide
Excess method of salt preparation
Involves the addition of an excess of an insoluble base (metal, metal oxide or metal carbonate).
Insoluble base + acid reaction
insoluble base + acid → soluble salt
Steps for excess method of salt preparation
- Warm the acid
- Add the insoluble base to excess to ensure all the acid has reacted
- Filter off the excess insoluble base
- Heat solution to evaporate half of the water
- Leave to cool and crystallise
- Dry the crystals
Why is the insoluble base added to excess in the excess method of salt preparation?
To make sure all of the acid reacts.
Titration method for salt preparation
Involves the addition of an acid to an alkali using a burette.
Titration reaction
soluble base (alkali) + acid → soluble salt + water
Steps for titration method of salt preparation
- Add acid in a conical flask using a volumetric pipette
- Fill a burette with alkali
- Add an indicator to the conical flask
- Add the alkali into the acid, slowly near the end point to find the exact volume required for neutralisation
- Repeat without the indicator
- Heat the solution to evaporate half of the water
- Leave to cool and crystallise
- Dry the crystals
Precipitation method for salt preparation (for insoluble salts)
Mix together solutions of two soluble salts to provide the ions needed.
Precipitation reaction
soluble salt + soluble salt → insoluble salt (residue) + soluble salt (filtrate)
Test for oxygen gas
Accelerates combustion reactions and relights a glowing splint.
Test for hydrogen gas
Reacts with oxygen in the air when exposed to a flame and combusts (burns) with a squeaky pop.
Test for carbon dioxide gas
Reacts with calcium hydroxide (limewater) to produce calcium carbonate, turning clear and colourless limewater milky/cloudy.
Test for ammonia gas
Reacts with litmus, turning damp red litmus paper blue.
Test for chlorine gas
Reacts with litmus, turning damp blue litmus paper red and then white/bleached.
Ammonia gas characteristics
No colour, pungent (strong & nasty) smell like rotten nappies.
Chlorine gas characteristics
Greenish-yellow gas with a pungent choking smell, like swimming pools.
Flame test for lithium (Li+)
Red.
Flame test for potassium (K+)
Lilac.
Flame test for sodium (Na+)
Yellow.
Flame test for copper (Cu2+)
Blue-green.
Precipitation reactions to test for cations
When you react some cations with hydroxide or ammonia solution, a coloured precipitate can form.
