Edexcel A level Chemistry Practical 2024
Exam Completely 100% Solved
overall equation: CaCO3 + 2CH3COOH --> Ca(CH3COO)2 +
CO2 + H20
Measure the gas evolved through an inverted cylinder or with a
gas syringe.
A weak acid is used to make the reaction slower so less gas is
lost at a time - Answer>>1)a. Measure the molar volume of a
gas (topic 5.2)
trying to prove Avogadro's law: The molar volume of any gas at
STP (298K and 1atm/101 kPa) is = 24dm^3
Errors:
Gas loss due to bung not being air tight, or some escapes when
the marble chips are added.
CO2 is slightly soluble in water so exact volume is unknown.
Weighing by difference ensures exact amount of CaCO3 added is
known. - Answer>>1)b. Measure the molar volume of a gas-
purpose and errors
Outline of method: weight by difference solid acid.
Dissolve in deionized water.
Transfer to a volumetric flask and fill to mark. Don't forget to add
washings.
Invert to mix
key points:
acid must have high molar mass to reduce weighing errors.
sample must be pure and not air sensitive - Answer>>2)a.
prepare a standard solution of a solid acid salt (topic 5.3)
3)a. prepare a standard solution of NaOH (same applies just
different salt)
, Outline of method:
Clean apparatus with deionized water and a little bit of the titrate
to cover the burette and analyte to cover pipette to reduce
dilution.
Pipette an aliquot of the analyte into a conical flask. Add indicator.
Titrate until concordant results are reached.
In calculations use mean titre. - Answer>>2)b. titrate the acid
solution against NaOH to find the concentration of NaOH
3)b. titrate the standardised NaOH against HCL to find the
unknown concentration of the HCL (same applies just used
phenolphthalein as indicator and have NaOH in the burette)
Swirl the flask between addition to ensure it mixes properly.
use a white tile to make colour change clearer
Wash down the walls of the flask with distilled water to make sure
all of the titrant reacts with the analyte.
Read the bottom of the meniscus at eye level (reduce parallax
error).
Calibrate pipette by ensure there are no air bubbles.
If phenolphthalein is used, the reaction mixture will turn go
colourless if left to stand/swirled. As NaOH reacts with CO2 in the
air. So if pink colour persists for 5 seconds- end point has been
reached - Answer>>2)c. find the concentration of NaOH-
titration errors
3)c. find the concentration of HCL- titration errors
Set up 3 test tubes of ethanol and two drops of the different
haloalkanes in the separate test tubes.
Place them in a water bath (50-60 degrees centigrade) with a
separate test tube of silver nitrate. Leave them until they all reach
the same temp.
Quickly add silver nitrate into each test tube (equal amounts as
ethanol) and start a stopwatch.
Measure and record the time taken for the ppts to form.
Exam Completely 100% Solved
overall equation: CaCO3 + 2CH3COOH --> Ca(CH3COO)2 +
CO2 + H20
Measure the gas evolved through an inverted cylinder or with a
gas syringe.
A weak acid is used to make the reaction slower so less gas is
lost at a time - Answer>>1)a. Measure the molar volume of a
gas (topic 5.2)
trying to prove Avogadro's law: The molar volume of any gas at
STP (298K and 1atm/101 kPa) is = 24dm^3
Errors:
Gas loss due to bung not being air tight, or some escapes when
the marble chips are added.
CO2 is slightly soluble in water so exact volume is unknown.
Weighing by difference ensures exact amount of CaCO3 added is
known. - Answer>>1)b. Measure the molar volume of a gas-
purpose and errors
Outline of method: weight by difference solid acid.
Dissolve in deionized water.
Transfer to a volumetric flask and fill to mark. Don't forget to add
washings.
Invert to mix
key points:
acid must have high molar mass to reduce weighing errors.
sample must be pure and not air sensitive - Answer>>2)a.
prepare a standard solution of a solid acid salt (topic 5.3)
3)a. prepare a standard solution of NaOH (same applies just
different salt)
, Outline of method:
Clean apparatus with deionized water and a little bit of the titrate
to cover the burette and analyte to cover pipette to reduce
dilution.
Pipette an aliquot of the analyte into a conical flask. Add indicator.
Titrate until concordant results are reached.
In calculations use mean titre. - Answer>>2)b. titrate the acid
solution against NaOH to find the concentration of NaOH
3)b. titrate the standardised NaOH against HCL to find the
unknown concentration of the HCL (same applies just used
phenolphthalein as indicator and have NaOH in the burette)
Swirl the flask between addition to ensure it mixes properly.
use a white tile to make colour change clearer
Wash down the walls of the flask with distilled water to make sure
all of the titrant reacts with the analyte.
Read the bottom of the meniscus at eye level (reduce parallax
error).
Calibrate pipette by ensure there are no air bubbles.
If phenolphthalein is used, the reaction mixture will turn go
colourless if left to stand/swirled. As NaOH reacts with CO2 in the
air. So if pink colour persists for 5 seconds- end point has been
reached - Answer>>2)c. find the concentration of NaOH-
titration errors
3)c. find the concentration of HCL- titration errors
Set up 3 test tubes of ethanol and two drops of the different
haloalkanes in the separate test tubes.
Place them in a water bath (50-60 degrees centigrade) with a
separate test tube of silver nitrate. Leave them until they all reach
the same temp.
Quickly add silver nitrate into each test tube (equal amounts as
ethanol) and start a stopwatch.
Measure and record the time taken for the ppts to form.
