chemistry paper 1 acids/alkalis Flashcards
what do international symbols on chemicals show?
the hazards associated with handling those particular solutions and they indicate the precautions needed when handling them.
what is an indicator?
how can the pH of a solution be found?
universal indicator?
substance that changes colour depending on the pH
using an indicator
is made from a mixture of different indicators and produces a range of colours depending on the pH
polyatomic ions are formed…
when small groups of atoms held together by covalent bonds loose or gain electrons.
what do acids and alkalis produce an excess of when dissolved in water?
acids - hydrogen ions (H+)
alkali - hydroxide ions (OH-)
The higher the number of hydrogen ions in a certain volume….
the higher the concentration of hydroxide ions ..
the higher their concentration. The more acidic the solution and lower the pH.
the more alkaline the solution and the higher the pH
concentrated solution
dilute solution
contain alot of dissolved solute per unit volume
contain a small amount of solute per unit volume
more concentrated acids…
contain more hydrogen ions so they will react faster with eg. magnesium metal
what does the pH of a solution measure? (acids)
the concentration of hydrogen (H+) ions
what happnes with strong acids?
weak acids
their molecules dissociate completely into ions when dissolved in water, producing higher concs of H+ ions
don’t dissociate completely
what is a base?
substances that neutralise acids to form a salt and water. All metal oxides are bases.
what happens during neutralisation?
hydrogen ions in the acid combine with oxide ions to form WATER. This removes hydorgen ions so the pH will increase and become more neutral.
the SALT is produced by replacing hydrogen ions with metal ions.
(1) The reaction between an acid and insoluble metal oxide ion…
can be used to prepare samples of different soluble salts
(2) if if soluble salts are prepared from an acid and an
insoluble reactant why..
is excess of the reactant is added
the excess reactant removed
the solution remaining is only salt and wate
-to make sure all the acid is used up
-to mkae sure the prepared salt is pure
-so water can cyrstalise leaving just salt
if a base can dissolve in water it makes it..
alkali
in a neutralisation reaction H+ and OH- ions form water and the other ions..
stay in solution as ions of the dissolved salt
how can you obtain dry soluble salts from its solution? (alkali)
why should it be neutral?
by crystallisation
otherwise youll contaminate the salt with an excess of one reactant
what is used to obtain a neutral solution?
(mixing an acid and alkali in correct amounts)
titration
how do you make pure dry saluble salt from alkali using titration
-carry out a titration
-note the volume of acid needed to neutralise the alkali
-use burette to add correct volume of acid without indicator
-evap water from solution formed
what happens when acids react with SOME metals?
the metal atoms react with hydrogen ions to form metal ions and hydrogen molecules
metal + acid ——–salt + hydrogen
what happens when acids react with metal carbonates?
they form a salt, water and carbon dioxide.
test for carbon dioxide.
bubble the gas through limewater, the limewater turns milky if co2 is present
test for hydrogen
Place a lighted splint in the tube of gas. (1)
If there is a squeaky pop, this proves that hydrogen
is present.
what is a precipotation reaction?
soluble substances in solutions cause and insoluble precipitate to form.
what substances are soluble in water?
-sodium potassium and ammonium salts, hydroxides and carobnates
-nitrates, most chlorides and sulphates
what substances are insoluble?
silver, lead chlorides,
lead barium and calcium sulfates
if both products are soluble in solution…
insoluble..
an insoluble precipitate will form.
precipate will form
how do u prepare insoluble salts?
-mix solutions in beaker then filture mixture
-rinse beaker w lil distilled water, pour this through funnel
-remove filter paper containing precip and dry in warm oven
