Chemistry Experiments
Organic
2026 Mock
(a) to ensure the ethanol was not evaporated
to bring reaction to completion without losing ethanol
(b) saponification / substitution
c) acted a solvent ✓
some of the soap was dissolved in the ethanol ✓ → to increase yield by allowing soap to precipitate
(d) X = brine ✓
to remove any solvents dissolved in soap that are soluble in brine, as soap is not soluble in brine ✓
precipitate the soap
(e) Y = glycerol ✓ or propane-1,2,3-triol
(f) diagram
(g) (i) 0.0125M ✓
(ii) 10.425g ✓
(iii) 7.2975g ✓
2021
(a) (i) to bring the reaction to completion and ensure no loss of the solvent ethanol ✓
(ii) water bath heated with a Bunsen burner
(iii) water bath indirectly heats the reaction mixture and maximises yield of soap
temperature is easily controlled
(iv) to maximise the yield of soap as some is dissolved in the ethanol ✓
(b) (i) glycerol ✓
(ii) a saturated solution of salt in water ✓
(iii) reaction mixture is poured into a beaker of brine solution.
soap is not soluble in brine and is precipitated out ✓
excess NaOH is dissolved in the brine
c) (i) the brine solution is passed through a Buchner funnel and filter paper
the soap remains in the Buchner funnel
filtration
(ii) the excess NaOH is in the filtrate ✓which passes through the filter paper into the Buchner flask
(d) the polar head of the soap molecules are attracted to polar molecules such as water, allowing the soap to dissolve in water ✓
one end of the soap molecule is polar
(e) 19.98g ✓
2024
(a) (i) benzoic acid is not very soluble in water
benzoic acid has low solubility in cold water
b.a has high solubility in warm water
(ii) to ensure benzoic acid does not crystallise in Buchner funnel
to remove insoluble impurities
(iii) fluted filter paper has a greater surface area ✓
the apparatus is warmed so it does not crack with sudden temperature change
(iv) to allow benzoic acid to recrystallise ✓
to maximise the yield
(v) it has a smaller temperature range than impure benzoic acid
melting point is over a narrow range
(b) (i) acidified potassium manganate (VII) ✓
Tollen’s reagent ✓
Fehling’s reagent ✓
(ii) acidified KMnO4: purple → colourless ✓
Tollens reagent: colourless → silver mirror forming in test-tube ✓
Fehling’s solution: royal blue → brick-red precipitate ✓
(iii) Mn2+ ETHANOIC ACID
Ag precipitate
Cu precipitate
(iv) ✓
c) (i) sunflower oil ✓
NaOH ✓
ethanol only a solvent
(ii) ethanol ✓
(iii) glycerol ✓
2023
(a) (i) diagram ✓
(ii) calcium carbide is not available in a pure state and contains impurities
air is present
(b) (i) solution turned from red → colourless ✓
(ii) solution turned from purple → colourless ✓
(iii) ethyne is a unsaturated compound ✓
c) (i) a lit taper is placed in a test tube of ethyne gas under a fume hood ✓
(ii) luminous yellow with a lot of soot ✓
(iii) ✓
(iv) burns with a hotter, clean, blue flame ✓
(d) 0.56 litres ✓
2023 def.
(a) (i) ethene ✓
(ii) solution turns from purple → colourless ✓
both compounds are unsaturated compounds ✓
(b) (i) ethanoic acid ✓
(ii)
(iii) ethanal ✓
(iv) Fehling’s A and Fehling’s B swirled together in a test tube to make Fehling’s solution
few drops of the liquid are added to the test tube
test tube gently warmed and shaken
a brick-red precipitate forms in the royal blue solution
the precipitate confirms the presence of ethanal ✓
c) (i) crystals are crushed using a pestle and mortar
one end of a capillary tube sealed with the blue flame of a Bunsen burner
a capillary tube is filled with crystals until they are about 1cm³ from bottom of tube
capillary tube placed in an aluminium block
block is heated with blue flame of Bunsen burner
temperature that crystals begin to melt is recorded
temperature that crystals have completely melted at is recorded
this is the melting point range of the benzoic acid ✓
(ii) recrystallised benzoic acid has a narrower melting point range than the impure benzoic acid
purer crystals have a sharper melting point
(iii) 81.03% ✓
(iv) hot filtration removes insoluble impurities ✓
2023 Mock
(a) acidified KMnO4 is added to a test tube of liquid sample
solution is gently warmed in a water bath and shaken
the solution turns from purple → colourless if the solution is propanal.
no change is observed if the solution is propanone ✓
(b) (i) ethanoic acid ✓
(ii) colourless → silver mirror formed in test tube
orange → green
c)
(d) H2O ✓
CaC2 ✓
(e) saturated compounds are compounds that contain one or more double carbon-carbon bonds ✓
(f) a luminous yellow flame with a great amount of soot ✓
2022
(a) (i) remove rubber tube from water before removing heat source ✓
(ii) do not directly heat the ethanol
ensure ethene product does not come into contact with flame
(b) (i) purple → colourless ✓
(ii) red → colourless ✓
(iii) addition
(iv) 1,2-dibromoethane ✓
c) X - charcoal ✓
Y - benzoic acid crystals ✓
Z - potassium chloride ✓
(ii) conical flask is placed in ice-water ✓
(iii) benzoic acid is dried overnight on the filter paper ✓
(iv) recrystallised sample of benzoic acid has a sharper melting point ✓
2022 def.
c) (i) X
(ii) bromine water is added to a test tube of ethyne
the solution’s colour changes from red → colourless, indicating ethyne is a saturated compound ✓
(iii) oxyacetylene welding ✓
2020
(a) (i) colourless ✓
(ii) graduated cylinder ✓
graduated syringe
(b) purple → brown ✓
c) D - the black specs are dissolved by the Na2SO3 ✓
Mn4+ reduced to soluble Mn2+
E - the white crystals of benzoic acid are visible in the conical flask ✓
crystallisation of benzoic acid
(d) (i) recrystallisation ✓
(ii) fill capillary tube with recrystallised benzoic acid sample
capillary tube placed into aluminium melting point block
aluminium melting point block placed on a hotplate
temperature at which crystals begin melting at recorded
temperature at which crystals have completely melted is recorded
this is the melting range of the benzoic acid crystals ✓
(e) (i) yes - ratio should be 4:3, actual ratio is 4.16:3
0.02 moles of KMnO4 sufficient
(ii) 1.7568g ✓
2020 Mock
(a) purple → brown ✓
Mn7+ is reduced to Mn4+, which forms a brown precipitate ✓
(b) benzoic acid X benzaldehyde
c) to dissolve the brown precipitate in the flask
to dissolve impurities
(d)
(e)
(f)
(g)
(h) (i) 2.1106g ✓
(ii) 57.8% ✓
2019
(a) (i) fizzing ✓
(ii) H2 and (CH3COO)2Mg ✓
(b) Fehling’s solution added to a test tube with 1cm³ of ethanal
test tube is warmed gently in a water bath and shaken
a brick-red precipitate forms in the royal blue solution ✓
c) (i)
(ii) Al2O3, a white solid ✓
(iii) if the rubber tube is not removed from the water before the heat source is removed a temporary vacuum is created. Suck-back occurs, sucking cold water into the very hot glass test tube. the sudden change in temperature may cause it to shatter. ✓
the rubber tube must be removed from water before the heat source is removed
(iv) 0.315 litres ✓
2019 Mock
(a) to bring the reaction to completion and ensure no loss of the solvent ethanol ✓
(b) substitution ✓
c) to act as a solvent ✓
to maximise the yield of soap, as some is dissolved in the ethanol ✓
(d) X - brine ✓
to precipitate out the soap, as soap is insoluble in brine ✓
(e) Y - glycerol ✓
in the filtrate ✓of the final filtration to isolate soap
(f) ✓
(g) 5 × 10^-3 moles ✓
0.015 moles ✓
0.0105 moles → 2.919g ✓
2018
(a) (i) Liebig condenser ✓
(ii) to bring the reaction to completion and prevent the loss of the solvent ethanol ✓
(iii) reactants: NaOH and sunflower oil ✓
solvent: ethanol ✓
(b) (i) a mixture of 2 immiscible liquids ✓
(ii) cyclohexane ✓
(iii) open stopper regularly
(iv) distillation ✓
(v) 3.15% ✓
c) (i) there are no insoluble impurities present in the solution ✓
(ii) maximises the yield of benzoic acid crystals
helps dry the crystals / faster
(iii) by comparing the melting point ranges of the impure and recrystallised benzoic acid
the recrystallised benzoic acid has a sharper melting point ✓
2018 Mock
(a) purple → brown ✓
Mn7+ reduced to Mn4+ ✓
(b) benzaldehyde ✓
c) convert sodium benzoate to benzoic acid
provide an acidic medium for Mn4+ to reduce to soluble Mn2+ ✓
(d) using litmus paper, which turns red in the acid
use pH meter, reading should be less than pH7
/ dip rod into the solution and touch it off moist blue litmus paper. litmus paper turns red in an acid.
(e) to dissolve the black specks of Mn4+ to soluble Mn2+ ✓
(f) to crystallise the benzoic acid
ensure all benzoic acid crystallises out of solution
(g) on the filter paper, left to dry overnight ✓
(h) (i) 2.1106g ✓
(ii) 57.8% ✓
2017
(a) (i) fizzing ✓
(ii) contaminated with air ✓
(b) (i) diagram ✓
(ii) remove the rubber tube from water before removing heat source
to prevent suck back of the water into the test tube and the glass test tube shattering from sudden temperature change ✓
tie back long hair around open flame of Bunsen burner to prevent it catching fire ✓
c) (i) ethene burns with a luminous yellow flame that has a small amount of soot ✓
ethyne burns with a luminous yellow flame and a great amount of soot ✓
compare: ethyne burns with a sootier flame than ethene
(ii)
(d) bromine water ✓
(e) 0.05 moles → 3×10^22 molecules ✓
Other
2026
(a) volatile liquid: a liquid with a low boiling point ✓
relative molecular mass: the average mass numbers of the isotopes of an element as they occur naturally, taking their abundances into account, based on the mass of the 1/12th carbon-12 isotope.✓
(b) (i) 1. find mass of a clean, dry conical flask, rubber band and aluminium foil using an electronic balance.
2. add 10cm³ of volatile liquid into conical flask
3. place aluminium foil over mouth of flask. hold in place with rubber band. pierce pin hole in foil
4. clamp flask in beaker of boiling water until all volatile liquid has evaporated
5. temperature of boiling water measured with a thermometer
6. atmospheric pressure measured with barometer
7. flask removed from water and allowed to cool
8. outside of flask and foil dried
9. find new mass flask (containing volatile liquid vapour), foil, and rubber band
10. subtract final mass from initial mass. the difference is the mass of the volatile liquid vapour
11. volume of container (conical flask) found by filling it completely with water and pouring contents into a graduated cylinder. ✓
c) barometer ✓
(d) 2.503 ×10^-3 moles ✓
(e) 83.899 → 84g
Mock 2025
(a) find the mass of a piece of filter paper ✓
known volume of water sample is filtered through filter paper a number of times.
allow the filter paper to dry overnight ✓
find the new mass of the filter paper ✓
the final mass - the initial mass of filter paper = the mass of suspended solids in the water sample ✓
multiply the mass in grams by 1000 to get in p.p.m and therefore, the concentration of the suspended solids in water sample
(b) 0.3438g ✓
c) the temporary hardness of the water was removed by boiling ✓
(d) dpd tablet ✓
dpd tablet dissolved in water sample and stirred.
dpd reacts with chlorine in water and turns pink
pour into test
place in comparator and compare with a control test tube of colourless water
turn precalibrated coloured disk until colour of control test tube matches the colour of the sample
read the reading shown for p.p.m of free chlorine in sample ✓
(e) (i) wooden splint is soaked in water sample overnight
damp wooden splint is dipped in salt
splint is held over the flame of a bunsen burner
if barium is present the flame will burn with a green flame
(ii) cold, freshly prepared FeSO4 is added to a test tube of sample.
concentrated sulfuric acid dripped trickled down the side of the test tube.
a brown ring forms at the junction of the liquids if nitrate ion is present ✓
2024
(a) (i) the conical flask containing the sodium thiosulfate is placed on a piece of paper with an X clearly visible through the bottom of the flask
HCl is added to conical flask
the mass of sulfur has been precipitated when the X at the bottom of the flask is no longer visible through the solution. ✓
(ii) 0.1M solution is diluted with deionised water
90 cm³ of 0.1M solution made up to 100cm³ with water
(b) (i) 0.016 ✓
0.014 ✓
0.012✓
0.01✓
0.008✓
0.006✓
(iii) as the concentration of the sodium thiosulfate increases so does the rate of reaction.
directly proportional relationship between rate of reaction and concentration ✓
c) (i) 0.0029 s^-1 ✓
(ii) 344.8s ✓
(d) (i) heat reactants in a water bath ✓
(ii) T2 is highest temperature ✓
increase in temperature increases the rate of reaction, taking less time for the mass of sulfur to precipitate ✓ least time for sulfur to precipitate
2024 Mock
(a) volatile liquid: a liquid with a low boiling point ✓
relative molecular mass: the average mass numbers of the isotopes of an element as they occur naturally, taking their abundances into account based on the 1/12th mass of the carbon-12 isotope ✓
(b) 1. find mass of a clean, dry conical flask, rubber band and aluminium foil
2. add 10cm³ of volatile liquid to conical flask
3. cover mouth of conical flask with aluminium foil, securing in place with rubber band. pierce a pinhole in the aluminium foil.
4. heat conical flask in a beaker of water until all of volatile liquid has evaporated
5. remove the conical flask from the water and allow it to cool
6. dry the outside of the conical flask
7. find the new mass of the conical flask, aluminium foil, rubber band
8. subtract the initial mass of the beaker from the final mass of the beaker. the difference is the mass of the volatile liquid vapour ✓
temperature of the water is measured with a thermometer ✓
the volume of the container is measured by filling the conical flask completely with water and pouring contents into a graduated cylinder ✓
c) barometer ✓
2023
(a) heat change when all the moles of reactants indicated in the balanced equation for the reaction react completely ✓
(b) (i) very accurate volume reading of 50cm³ ✓
(ii) process of adding base to cup is too slow ✓
c) (i) neutralisation is an exothermic reaction ✓
(ii) heat loss due to surroundings ✓
(iii) polystyrene is a better insulator of heat than glass ✓
(d) (i) 0.05 moles ✓
(ii) 1.428 kJ
(iii)
(e) (i) more concentrated solutions give out greater heat of reaction which is easier to detect and measure.
bigger temperature rise recorded
(ii) no change in molarity of reactants X 3 times more moles neutralised
2023 Mock
(a) exothermic ✓
temperature of mixture rose by 6.8K ✓
(b) (i) for accuracy to ensure the mixture is the same temperature throughout before taking a reading ✓ distribute heat evenly
(ii) heat loss to surroundings ✓
(iii) heat given out by reaction would be too small to record accurately
c) burette: accurate volume reading ✓
too slow to add base to cup ✓
(d) the heat change when the number of moles of reactants indicated in the balanced equation for the reaction react completely ✓
(e) (i) 0.09 moles ✓
(ii) 5.1408 kJ ✓
(iii) 57.1 kJ / mol✓
(f) corrosive: test tube of solution being poured on hand ✓
2022
(a)
(b) corrosive ✓
avoid contact with the skin and eyes ✓
c) (i) 14 minutes ✓
(ii) 20 cm³ / minute
(iii) 10 cm³ / minute
(d) (i) rate is proportional to concentration
if concentration is halved then rate of reaction is halved
112 / 2 = 56cm³
(ii) catalyst has a greater surface area
catalyst quantity has no effect on yield
2023 def.
(a) (i) oxidising reagent
(ii) do not store in glass bottles ✓
(iii) black powder ✓
(b) (i) 0.02 moles ✓
(ii) 0.24 litres ✓
(iii) graduated cylinder ✓
(iv) diagram ✓
c) (i)
(ii) 0.323 cm³ / s ✓
2022 def.
(a) ✓
the catalyst is quickly added to the conical flask of H2O2 and the flask is immediately stoppered
mix by rotating the conical flask
(b) MnO2 ✓
heterogeneous catalysis ✓
the reactant and the catalyst are in different phases. H2O2 is a liquid and MnO2 is a solid. ✓
c) graph ✓
(d) (i) 1.5 minutes ✓
(ii) 4.138 cm³ / minute ✓
(e) half the concentration of the reactants equals half the concentration of the products ✓
2021
(a) a damp wooden splint is dipped into each salt
the wooden splint is held over the blue flame of a Bunsen burner
sodium burns with a yellow flame
barium burns with a green flame ✓
(b) (i) BaCl2 added to a test tube of sodium sulfite solution
a white precipitate forms
dilute HCl added to the test tube
the white precipitate dissolves
if the white precipitate remains and only dissolves when solution is heated, sulfate ion is present ✓
(ii) no change observed X red solution → colourless
BaCl2 is added to the solution in test-tube
white precipitate forms that does not dissolve in dilute HCl
this shows the sulfite ion has been oxidised to the sulfate ion ✓
c) (i) magnesium is a good reducing agent in the reaction with copper
magnesium loses electrons more easily than copper
(ii) zinc is not as good of a reducing agent as magnesium in the reaction with copper metal
zinc loses electrons more easily than copper
(iii) Mg + Cu2+ → Mg2+ + Cu
(iv) zinc is the limiting reagent of the reaction ✓
2021
(a) a damp wooden splint dipped is dipped into each salt
each wooden splint is held over the blue flame of a Bunsen burner
if sample burns with a blue-green flame, the copper ion is present
if sample burns with a crimson flame, the lithium ion is present ✓
(b) (i) copper (II) nitrate ✓
(ii) freshly prepared, cold FeSO4 was added to a test tube of the copper (II) nitrate salt.
concentrated sulfuric acid is trickled down the side of the test tube.
a brown ring forms at the junction of the 2 liquids, indicating a positive result for the nitrate ion ✓
c) (i) sodium chloride ✓
(ii) a white precipitate which is soluble in dilute ammonia solution ✓
(d) (i) sodium sulfate and potassium sulfite ✓
(ii) dilute HCl ✓
(e) (i) Na2HPO4.12H2O ✓
(ii) yellow precipitate forms ✓
2020
(a) reactants are heated in a water bath
flask with Na2SO3 heated in water bath set to known temperature on hot plate
add HCl and mix
use thermometer to record reaction mixture temperature
(b) (i) the colourless solution turned cloudy
colourless → cloudy, yellow solution
(ii) the conical flask was placed on paper with a cross
stand flask on piece of paper with a cross marked
record time for cross to become obscured
when the colourless solution has completely obscured the X to the point it is no longer visible in the bottom of the conical flask, the reaction is said to be completed
c) (i) 0.005 ✓
0.009 ✓
0.018 ✓
0.029 ✓
0.063 ✓
0.111 ✓
(d) (i) graph
(ii) 11 C ✓
(iii) the graph is an exponential graph X more effective collisions at higher temperature increase rate of reaction
(e) (ii) not on the curve ✓
(iii) greater than the original flask X lower
smaller rate of reaction in Run 8 than in previous run for same temperature
deeper flask reduces the surface area for reaction to occur and reduces the rate of reaction
rate of reaction appears to be smaller
2020 Mock
(a) change in concentration / time taken for change in concentration to occur
the change in concentration per unit time of any one reactant or product
(b) graph
c) (i) Run B ✓
(ii) Run B ✓
(d) Run A - 0.684
Run B - 0.565
rates of reaction for the reactions are different
slower rate in B as reaction is almost complete at 3 minutes
faster rate in A as reaction is slower at 3 minutes
(e) the shape of the marble chips from each supplier was different.
Run B used marble chips with a greater surface area than Run A ✓