1) Chemical Changes Flashcards
what are acids in solutions sources of?
hydrogen ions H+
what are alkalis in a solution sources of?
hydroxide ions OH-
what is the pH of acidic solutions?
lower than 7
what is the pH of alkalis solutions?
above 7
what colour is litmus in different acid, neutral and alkalis solutions?
acid= red neutral= purple alkalis= blue
what colour is methyl orange in different acid, neutral and alkalis solutions?
acid= red neutral= yellow alkalis= yellow
what colour is phenolphthalein in different acid, neutral and alkalis solutions?
acid= colourless neutral= colourless alkalis= pink
the higher the concentration of hydrogen ions in an acid solution…
the lower the pH
the higher the concentration of hydroxide ions in an alkaline solution…
the higher the pH
what is the method for investigating the neutralisation reaction between calcium oxide(base) ad adult hydrochloric acid?
- measure out dilute hydrochloric acid into conical flask
- measure fixed mass of calcium oxide, scales
- add together
- wait for base to completely react, record pH
- repeat 2-4 until all acid reacted
- plot graph to see how pH changes with mass of base added
what is concentration?
- how much acid there is in al litre 1dm3 of water
- how watered down the acid is
what is dilute?
acid with small number of acid molecules compared to volume of water
what is a strong acid?
- ionise almost completely in water
- hydrocloric acid, nitric acid, sulfuric acid
what is a weak acid?
- do not fully ionise in solution
- citric acid, carbonic acids
what is a base?
any substance that reacts with an acid to form a salt and water only
what are alkalis?
soluble bases
acid + metal =
salt hydrogen
metal oxides + acid=
salt + water
metal hydroxides + acid=
salt + water
metal carbonates + acid=
salt + water + carbon dioxide
what is the chemical test for hydrogen?
- lightened splint
- makes sneaky pop
what is the chemical test for carbon dioxide?
- bubbling it through limewater
- it will turn cloudy
what is neutralisation reaction?
is a reaction between an acid and a base
what is an acid-alkali reaction?
when hydrogen ions (H+) from the acid react with hydroxide ion(OH-) from the alkali to form water
how do you make soluble salts using an acid and insoluble base?
- heat acid in water bath-speeds up reaction
- add base to acid- form a soluble salt
- you will know when it all has been naturalised when the excess solid will just skink to the bottom
- filter of solid to leave salt and water
how can you make soluble salts using acid/alakali and a soluble reactant?
- set amount of acid measured using pipette, add indicator
- slowly add alkali to acid until reached end point using burette, when indicator changes colour so its neutralised
- carry out reaction using same volumes of alkali and acid but no indicator
- salt and water left
- evaporate to leave pure, dry salt
are common sodium, potassium and ammonium salts soluble or insoluble?
soluble
are nitrates soluble or insoluble?
soluble
are common chlorides soluble or insoluble?
soluble
except silver chloride and lead chloride
are common sulphates soluble or insoluble?
soluble
except lead, barium, calcium chloride
are common carbonates and hydroxides soluble or insoluble?
insoluble
expect sodium, potassium, ammonium
what is the method used to prepare a pure dry sample of an insoluble salt?
- use a precipitation reaction
1. 1 scapular of lead nitrate in test tube. add deionised water, till lead dissolved
2. same with sodium chloride
3. mix into beaker. stir.
4. use filterpaper filter it
5. tip sediment into new beaker and leave to dry
