AQA A LEVEL CHEM PRACTICALS – PAPER 3
5.0)
Terms in this set (35)
Titration - known concentration in - rinse burette with deionised water and then with the solution you're using -
burette, unknown concentration in fill the burette past the mark (using funnel) and empty the burette until meniscus is on
conical flask
the line
- removal funnel so no more solution can enter
- rinse pipette with deionised water and then with the solution you're using.
when filling pipette go past the line then empty until meniscus is on the line
- rinse conical flask with deionised water
- pipette 25cm³ of required solution into conical flask
- add required indicator
- swirl to mix
The- standardtitrate
cell potential is the
the solution e.m.f.
from thebetween
burette, two half
about cellsatmaking
1cm³ a time,up theindicator
until
cell,changes
measured under standard conditions.
colour
clean piece
*any of each
drops metal, up
or splashes e.g.the
copper and
side of zinc.
the degrease
flask using
should be propanone,
washed with
place copper in a
deionised waterbeaker with around 50cm
₃ 1moldm ⁻ ³ copper sulfate
solution, place zinc in a seperate beaker of same concentration and volume
*repeat titration adding solution dropwise when reaching end point - record
zincall
sulfate solution
to 2.d.p but only ending in 0 or .5 repeat until results are concordant
measuring e.m.f. of electrochemical
join(the two. beakers
within 1) with filter paper coated in NaCl/potassium nitrate - acts
cells
as a salt bridge
may lose some solution before it starts don't remove
connect one end to positive terminal of voltmeter and the other electrode to
funnel so some drops fall during titration
the negative terminal, ensuring the reading is positive - if it is negative,
What may go wrong with titration? may the
reverse rinse conical flask
connections to with solution so you have added more solution to
the electrodes
the flask may not include all of the washings
record the reading of the voltmeter, writing which electrode is connected to
the positive and negative terminals
strong acid - strong base = either methyl orange or phenolphthalein ( pink
- place a known mass of a sample in a beaker, add 100cm³m of distilled water
to colourless) weak acid - strong base = phenylphthalein, strong acid -
to beaker to dissolve sample, record mass to 2 d.p.
weak base = methyl orange ( yellow to red/orange)
- use a glass rod to stir
Which indicator should be used?
Indicator
- pour must change
this solution sharply at flask
into a graduated the equivilance
via a funnelpoint, so the pH range of the
indicator should fall within the 'vertical section' (region of rapid pH change)
standard solution - rinse beaker and funnel using distilled water and add washings to volumetric
flask
What happens in an acid-base titration - make up to
solution ofthe mark
alkali with distilled
of known water soadded
concentration that the meniscus
from sits
a burette toon the
a measured
lineamount of an acid. indicator used to find end point - from volume of base
required, concentration of acid can be calculated
- invert flask several times to ensure uniform solution
, titrate the aq solution, with known volume in a conical flask and acid
in burette, repeat titration until concordant results found. Use added
How can number of molecules of water volume to work out moles using molar ratio.
of crystallisation be determined in a
practical? calculate mr using known mass and number of moles found - then calculate
'x' using found mr - mr of each molecule in substance, divided by 18 to find
number of H2O molecules
- pipette 25cm³ acid and add indicatir, place beaker on a magnetic stirrer
and place magnet in the beaker, fill burette with base
- rinse electrode with distilled water as readings may have changed over
time, dip it into the acid in the beaker, recording pH
Acid-base titration - switch on stirrer and ensure magnet doesnt strike the electrode.
- add 5cm³ base and take readings of pH and indicator
- continue adding base taking 5cm³ readings each time then 1cm³ around
end point, then 5cm³ util most base has been added
- plot a graph of pH (Y axis) against volume of base added
This is an exothermic reaction so a cooling curve should be drawn.
- weigh a known mass of anhydrous copper sulfate (sample )
- using measuring cylinder, place 25cm³ deionised water into polystyrene
cup, place this in a beaker
- use thermometer to record temperature of deionised water every minute for
Using hess's law to determine enthalpy 15 minutes, stirring constantly (use stopwatch )
change of a reaction - calculating ∆1
- at FOURTH minute, add anyhdrous sample rapidly and continue to stir,
record temperature at 5 minutes then every minute until 15 mins.
plot graph of temp on Y against time, draw two seperate best fit lines and use
the graph to determine the temperature change at the fourth minute (rise in
temp) use this value in q=mc∆t
Using hess's law to determine enthalpy this is an ENDOTHERMIC reaction so max and min temperatures should be
change of a reaction - calculating ∆2 recorded
- weigh out mass of hydrated copper sulfate, using measuring
cylinder place 25 cm³ of deionised warer in a polystyrene cup (INSULATION)
and this in a beaker for support and additional insulation
- record temp of deionised water
- add hydrated sample to cup and stir, watch thermometer and
record the minimum temperature use temperature fall in q=mc∆t to find
enthalpy change for ∆h2
∆H3 = ∆H1 - ∆H2
5.0)
Terms in this set (35)
Titration - known concentration in - rinse burette with deionised water and then with the solution you're using -
burette, unknown concentration in fill the burette past the mark (using funnel) and empty the burette until meniscus is on
conical flask
the line
- removal funnel so no more solution can enter
- rinse pipette with deionised water and then with the solution you're using.
when filling pipette go past the line then empty until meniscus is on the line
- rinse conical flask with deionised water
- pipette 25cm³ of required solution into conical flask
- add required indicator
- swirl to mix
The- standardtitrate
cell potential is the
the solution e.m.f.
from thebetween
burette, two half
about cellsatmaking
1cm³ a time,up theindicator
until
cell,changes
measured under standard conditions.
colour
clean piece
*any of each
drops metal, up
or splashes e.g.the
copper and
side of zinc.
the degrease
flask using
should be propanone,
washed with
place copper in a
deionised waterbeaker with around 50cm
₃ 1moldm ⁻ ³ copper sulfate
solution, place zinc in a seperate beaker of same concentration and volume
*repeat titration adding solution dropwise when reaching end point - record
zincall
sulfate solution
to 2.d.p but only ending in 0 or .5 repeat until results are concordant
measuring e.m.f. of electrochemical
join(the two. beakers
within 1) with filter paper coated in NaCl/potassium nitrate - acts
cells
as a salt bridge
may lose some solution before it starts don't remove
connect one end to positive terminal of voltmeter and the other electrode to
funnel so some drops fall during titration
the negative terminal, ensuring the reading is positive - if it is negative,
What may go wrong with titration? may the
reverse rinse conical flask
connections to with solution so you have added more solution to
the electrodes
the flask may not include all of the washings
record the reading of the voltmeter, writing which electrode is connected to
the positive and negative terminals
strong acid - strong base = either methyl orange or phenolphthalein ( pink
- place a known mass of a sample in a beaker, add 100cm³m of distilled water
to colourless) weak acid - strong base = phenylphthalein, strong acid -
to beaker to dissolve sample, record mass to 2 d.p.
weak base = methyl orange ( yellow to red/orange)
- use a glass rod to stir
Which indicator should be used?
Indicator
- pour must change
this solution sharply at flask
into a graduated the equivilance
via a funnelpoint, so the pH range of the
indicator should fall within the 'vertical section' (region of rapid pH change)
standard solution - rinse beaker and funnel using distilled water and add washings to volumetric
flask
What happens in an acid-base titration - make up to
solution ofthe mark
alkali with distilled
of known water soadded
concentration that the meniscus
from sits
a burette toon the
a measured
lineamount of an acid. indicator used to find end point - from volume of base
required, concentration of acid can be calculated
- invert flask several times to ensure uniform solution
, titrate the aq solution, with known volume in a conical flask and acid
in burette, repeat titration until concordant results found. Use added
How can number of molecules of water volume to work out moles using molar ratio.
of crystallisation be determined in a
practical? calculate mr using known mass and number of moles found - then calculate
'x' using found mr - mr of each molecule in substance, divided by 18 to find
number of H2O molecules
- pipette 25cm³ acid and add indicatir, place beaker on a magnetic stirrer
and place magnet in the beaker, fill burette with base
- rinse electrode with distilled water as readings may have changed over
time, dip it into the acid in the beaker, recording pH
Acid-base titration - switch on stirrer and ensure magnet doesnt strike the electrode.
- add 5cm³ base and take readings of pH and indicator
- continue adding base taking 5cm³ readings each time then 1cm³ around
end point, then 5cm³ util most base has been added
- plot a graph of pH (Y axis) against volume of base added
This is an exothermic reaction so a cooling curve should be drawn.
- weigh a known mass of anhydrous copper sulfate (sample )
- using measuring cylinder, place 25cm³ deionised water into polystyrene
cup, place this in a beaker
- use thermometer to record temperature of deionised water every minute for
Using hess's law to determine enthalpy 15 minutes, stirring constantly (use stopwatch )
change of a reaction - calculating ∆1
- at FOURTH minute, add anyhdrous sample rapidly and continue to stir,
record temperature at 5 minutes then every minute until 15 mins.
plot graph of temp on Y against time, draw two seperate best fit lines and use
the graph to determine the temperature change at the fourth minute (rise in
temp) use this value in q=mc∆t
Using hess's law to determine enthalpy this is an ENDOTHERMIC reaction so max and min temperatures should be
change of a reaction - calculating ∆2 recorded
- weigh out mass of hydrated copper sulfate, using measuring
cylinder place 25 cm³ of deionised warer in a polystyrene cup (INSULATION)
and this in a beaker for support and additional insulation
- record temp of deionised water
- add hydrated sample to cup and stir, watch thermometer and
record the minimum temperature use temperature fall in q=mc∆t to find
enthalpy change for ∆h2
∆H3 = ∆H1 - ∆H2
