3.3 Acids & Alkalis Flashcards
what do acids produced when added to water?
H+ ions - proton donor
what do alkali’s produced when added to water?
OH- ions - proton acceptor - alkali is a soluble base
H+ ions relation to pH scale
strongly acidic (pH 0) - most H+ ions - 10⁰
- strongly alkali (pH 14) - least H+ ions - 10⁻¹⁴
- as numbers on pH scale go up by 1, number H+ ions decreases by a factor of 10
what do you use to measure the pH of something?
universal indicator
what does the number of hydrogen ions present in a solution depend on?
how ionised the acid is
what does ionisation mean?
ionised means how split up the acid is - when HCL splits up into H+ and Cl-
what happens when acid is partially ionised?
acid is only partially split up & hydrogen ion concentration is lower - weak acid
draw a concentrated strong acid
fully dissociated - many particles
draw a dilute strong acid
fully dissociated - not many particles
draw a concentrated weak acid
partially dissociated - many particles
draw a dilute weak acid
partially dissociated - not many particles
blue litmus paper & red solution shows
acidity in a substance
red litmus paper turns blue shows
alkalinity in a substance
substance is neutral pH
if litmus paper used - colour doesn’t change
- if litmus solution used - turns purple
neutralisation reaction
acid + base –> salt + water (+CO2)
ionic equation for formation of water
H+ (aq) + OH- (aq) –> H20 (l)
properties of salt
compound made of metal & non-metal
- v. high mpt
- dull + brittle
common bases
- metal carbonates
- metal oxides
- metal hydroxides
4 ways of making salts from acids:
acid + metal hydroxide –> salt + water
acid + metal oxide –> salt + water
acid + metal carbonate –> salt + water + CO2
(acid + metal –> salt + hydrogen)
reacting acid with metal (to make salt) - method
has to be more reactive than hydrogen - not too reactive though
reacting acid with base (to make salt) - method
insoluble - filtration + crystallisation
reacting acid with alkali (to make salt) - method
titration
reaction between 2 salt solutions to form an insoluble salt (to make salt) - method
precipitation, filtration, wash, dry
why do you use titration?
to make a neutralisation reaction between a base and an acid producing a salt without any excess
why do you do titration twice?
- 1st time - find amounts of reactants to use
- 2nd time - actual one
making copper sulfate from copper (II) oxide - making salts from insoluble bases
1 - add insoluble copper oxide to sulfuric acid + stir - warm gently
2 - solution turns blue as reaction occurs - shows copper sulfate is being formed
3 - when reaction complete - filter solution to remove excess copper oxide
4 - evaporate some of water from filtrate + leave to crystallise
how can insoluble salts be produced?
by mixing 2 soluble salt solutions together
- ions swap partners in the reaction in a displacement reaction
- the combinations of ions that produce an insoluble salt result in a precipitate forming (called precipitation reactions)
what type of salt is always soluble?
nitrates
what is the end point (titration)
- the point in titration where you have added the exact amount of acid / alkali where neutralisation occurs
