Studied by 52 peoplewhat are acids in solutions
sources of hydrogen ions
what are alkalis in solutions
sources of hydroxide ions
what is the pH of a neutral solution
pH 7
what is the pH of an acidic solution
less than pH 7
what is the pH of an alkaline solution
more than pH 7
what is the colour of litmus in an acidic solution
red / orange
what is the colour of litmus in a neutral solution
purple
what is the colour of litmus in an alkaline solution
blue
what is the colour of methyl orange in an acidic solution
red
what is the colour of methyl orange in a neutral solution
yellow
what is the colour of methyl orange in an alkaline solution
yellow
what is the colour of phenolpthalein in an acidic solution
colourless
what is the colour of phenolpthalein in a neutral solution
colourless
what is the colour of phenolpthalein in an alkaline solution
pink
what does a higher concentration of hydrogen ions lead to
a lower pH
what does a higher concentration of hydroxide ions lead to
a higher pH
what happens as the concentration of hydrogen ions increases by a factor of 10
the pH of the solution decreases by 1
what happens in the core practical investigating the change in pH when calcium hydroxide is added to a fixed volume of hydrochloric acid
the pH will stay low for the first half of the graph and then will rapidly increase. after this it will plateau as there are only a set number of pH values
what does dilute mean
a small amount of solute dissolved in a large volume of solvent
what does concentrated mean
a large amount of solute dissolved in a small volume of solvent
what does weak acid mean
an acidic solute that does not dissociate into its ions completely when dissolved
what does strong acid mean
an acidic solute that completely dissociates into it ions when dissolved
what is a base
any substance that reacts with an acid to form a salt and water only
what are alkalis
soluble bases
general reaction of metals to create salts
metal + acid → salt + hydrogen
general reaction of metal oxides to create salts
metal oxide + acid → salt + water
general reaction of metal hydroxides to create salts
metal hydroxide + acid → salt + water
general reaction of metal carbonates to create salts
metal carbonate + acid → salt + water + carbon dioxide
describe the chemical test for hydrogen
place a lighted splint in a test tube containing the gas. if hydrogen is present there will be a squeaky pop. this mini explosion is because hydrogen burns quickly in oxygen causing steam and releasing heat energy.
describe the chemical test for carbon dioxide
carbon dioxide reacts with calcium hydroxide to form a white precipitate of calcium carbonate. limewater is a solution of calcium hydroxide. if carbon dioxide is bubbled through limewater, the limewater will turn cloudy white.
neutralisation reactions
acid + base → salt + water (due to the strong attractions between the H+ ions and the OH- ions which form the water) (this will create a solution with a pH of 7)
why, if soluble salts are prepared from an acid and an insoluble reactant, is excess of the reactant added
to make sure all of the acid has reacted with the reactant
why, if soluble salts are prepared from an acid and an insoluble reactant, is the excess reactant removed
as the excess reactant does not have any acid to react with and is therefore not necessary in the reaction anymore
why, if soluble salts are prepared from an acid and an insoluble reactant, the solution remaining is only salt and water
the acid and insoluble reactant react together in a neutralisation reaction to form salt + water
why must titration be used when forming a soluble salt from an acid and an insoluble reactant
Titration must be used to obtain a solution of a salt and water only, when using an acid and an alkali. This is because there is no insoluble excess reactant that could be removed by filtration
after titration why are the acid and soluble reactant mixed in correct proportions
because you want no excess acid or the other reactant and precise amount of salt
describe how to carry out an acid-alkali titration
Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask.
Add a few drops of a suitable indicator and put the conical flask on a white tile.
Fill the burette with acid and note the starting volume.
Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading.
what sodium’s are soluble
all common ones
what potassium’s are soluble
all common ones
what ammonium’s are soluble
all common ones
what nitrate’s are soluble
all of them
what chloride’s are soluble
all common ones except silver and lead
what sulfate’s are soluble
all of them except for lead, barium and calcium
what carbonate’s are soluble
sodium, potassium and ammonium
what hydroxide’s are soluble
sodium, potassium and ammonium
Note
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