U1-3 - Acids and Bases Flashcards
What is a pH scale?
A measure of the hydrogen ion concentration in a solution.
Low pH = high concentration
Acidic solutions have pH…
less than 7.
Alkaline solutions have pH…
more than 7.
Neutral solutions have pH…
equal to 7.
Soluble metal oxides turn solution pH…
alkaline.
Soluble non-metal oxides turn solution pH…
acidic.
Insolube oxides turn solution pH…
neutral (no effect).
Environmental problems caused by non-metal oxide gases
Acid rain, ocean acidification, greenhouse effect.
Base
A substance which can neutralise an acid
Acid
Substance which contains hydrogen ions (H+)
Alkali
Soluble base
Neutralisation
A reaction between an acid and a base which produces a salt and water.
Metal oxide + Acid → …
Salt + Water
Metal hydroxide + Acid → …
Salt + Water
Metal carbonate + Acid → …
Salt + Water + Carbon dioxide
Sodium chloride is a salt.
Where does the ‘sodium’ part come from?
Parent base
(sodium oxide, hydroxide or carbonate)
Sodium chloride is a salt.
Where does the ‘chloride’ part come from?
Parent acid
(hydrochloric acid)
Phosphoric acid makes …. salts.
phosphate
Sulfuric acid makes …. salts.
sulfate
Formula for hydrochloric acid
HCl
Formula for sulfuric acid
H2SO4
Formula for phosphoric acid
H3PO4
Colour of universal indicator in acid
Red
(red/orange/yellow)
Colour of universal indicator in alkalis
Blue/purple
Colour of universal indicator in neutral solutions
Green
Colour of phenolphthalein in acidic and neutral solutions
Colourless
(NOT clear!)
Colour of phenolphthalein in alkaline solutions
Pink
Ions which make a solution acidic
H+ (hydrogen)
Ions which make a solution alkaline
OH– (hydroxide)
Why is water neutral?
Equal concentrations of H+ and OH– ions.
If an acid is diluted, the pH …
increases.
If an alkali is diluted, the pH …
decreases.
If a solution is diluted, the concentrations of H+ and OH– ions …
decrease.
Salt
An ionic compound in which the H+ ions of an acid have been replaced by metal ions.
Spectator ions
Ions which are unchanged by a chemical reaction.
E.g. Na+(aq) → Na+(aq)
How do we know which ions are spectator ions in a reaction?
Ions in the aqueous product are spectator ions.
A solution of accurately known concentration
Standard solution
What is the point of titration?
To find out an unknown concentration by reacting a sample with a standard solution.
During a titration, what tells you the reaction is finished?
The first permanent colour change
What is a titre?
Volume of solution added from the burette during a titration.
What are concordant titres?
Titres within 0.2 cm3 of each other.
Pipette
Burette
Titres within 0.2 cm3 of each other are called ….
concordant.
What is c1 and c2?
Concentrations of acid and base used in a titration.
What is V1 and V2?
Volumes of acid and base used in a titration.
Units must match, e.g. both in litres or both in cm3.
What is n1 and n2?
Number of moles of acid and base from the balanced equation.
