Topic 3- Part one Acids Flashcards
What are acids a source of?
Hydrogen ions
h+
What are alkali’s a source of?
Hydroxide ions
OH-
3 indicators?
-Methyl Orange
-Phenolphthalein
-Litmus
What colour does litmus turn?
universal indicator orange
1) Acid- Red
2) Alkali- Blue
What colour does Methyl Orange turn?
orannge
1) Acid- Red
2) Alkali- Yellow
What colour does phenolphthalein turn?
colourless
1) Acid- Colourless
2) Alkali- Pink
When is smth more acidic/alkali?
Higher conceentration of H+/OH- oins which lowers/increases the pH
How much does the concentration have to change for the pH by one
x10 (more H+/OH- ions)
Core Practical: Investigate the change in pH on adding by powdered calcium hydroxide or calcium oxide to a fixed volume
of dilute hydrochloric acid
1) Measure 50cm^3 of 1mol dm^-3 HCl into a beaker
2) Measure pH using universal indicator (gradual change)
3) Measure 0.25g calcium hydroxide
5) Add calcium hydroxide + measure pH
6)Repeat until total of 2.5g of calcium hydroxide added
more alkali as OH-
Concentrated vs dilute?
1) Larger amount of substance in given volume
2) Less
What is a strong acid?
One that fully dissociates (breaks down) into h+
HCl, HNO3
What is a weak acid?
-Doesnt fully dissociate
Ethanoic acid, CH3OOH
Acid + Base
a base is any substance that reacts with an acid to make?
—> salt + water
What are alkalis
soluable bases
Metal + Acid
—> Salt + Hydrogen
Metal oxide + Acid
—-> Salt + water
Metal Hydroxide + Acid
—-> Salt + Water
Metal carbonate + Acid
—-> Salt + water + carbon dioxide
Chemical test for Hydrogen?
-Place a burning splint into gas
-Will produce a squeaky pop sound if hydrogen
Chemical test for Carbon dioxide?
Bubble gas through limewater (calcium hydroxide) and goes cloudy
What is a neutralisation reaction?
Between acid + base (alkali)
Salt + water
What happens in a neutralisation reaction?
H+ and OH- ions react to form water
When we react insoluable salt + acid why do we add excess salt?
- Ensure all acid has reacted
salt is insoluable so wont react with water produced
How and why do we remove excess salt in insoluable reactant + acid reaction?
-Done by filtration
-leave only salt + water
What do we do if we want to produce a soluable salt from an insoluable reactant and acid?
1) Add excess insoluable salt (ensure all acid has reacted)
2) Filter off excess (insoluable so wont dissolve in produced water)
3) Evaporate water in water bath
What do we do if we want to produce a soluable salt from a soluable reactant and an acid?
- Titration (becuase exact measurement is needed as excess reactants are unable to be removed)
1) Add alkali solution into conical flask
2) Add indicator e.g phenolphthalein
3) Should be pink
4) Add Acid to titration buiret
5) Add drop by drop till colourless (neutral)
6) Use activated charcole to remove indicator
7) Filter of insoluable charcole + indicator
8) Heat + evaporate for salt crystals
Core practical: How to make copper sulphate from copper oxide?
1) Add excess copper oxide (insoluable) to sulphuric acid
2) Filter and filter paper to filter excess
3) Evaporate off water by placing in water bath
Which type of salts are all soluable?
all nitrates
Which type of salts are mostly soluable?
- Most sulfates
- Most Halogens (7 e.g chlorine/iodine)
Which sulfates are insoluable?
-Lead sulphate
-Barium sulphate
-Calcium sulphate
lead, barium, calcium
Which halogens ar insoluable?
- Reacted with silver or lead
Which carbonates and hydroxides are soluable?
-Sodium
-Potassium
-Ammonium
Which carbonates and hydroxides are insoluable?
All others apart from
-Sodium
-Potassium
-Ammonium
What are precipitates?
Insoluable solids formed from change in solution
e.g if a carbonate of hydroxide salt is formed it will be a precipitate
How to get insoluable salt?
1) Mix wanted solutions together
2) Filter for insoluble residue
3) Clean with distillled water
4) Leave to dry or evaporate using drying oven
