IGCSE CHEMISTRY EXAM 2025/2026
QUESTIONS AND ANSWERS 100% PASS
State the method used to obtain sand from a mixture of sand and water - ANS filtration
State the method used to obtain solid copper sulfate from aqueous copper sulfate -
ANS crystallisation
State the method used to obtain red food dye from a mixture of food dyes - ANS paper
chromatography
State the method used to obtain water from salt water - ANS simple distillation
Draw a diagram to show equipment used in simple distillation - ANS For what process is this
equipment used?
State the method used to obtain kerosene from a crude oil. - ANS fractional distillation
Draw the equipment used in fractional distillation in the lab - ANS For what process is this
equipment used?
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,Explain how fractional distillation is used to separate a mixture of different liquids - ANS The
different liquids have different boiling points
State the method used to extract the red dye from a sample of rose petals - ANS dissolving
Describe how pure salt can be obtained from rock salt - ANS 1) Grind rock salt into a fine
powder. 2) Add powder to hot water and stir to dissolve salt. 3) Filter mixture. Salt solution
passes through the filter paper leaving behind the sand. 4) Boil filtrate to evaporate some of the
water. 5) Leave saturated solution to cool so that crystals of salt form. 6) Filter cold mixture to
separate the crystals from the remaining solution.
Ethanol is a flammable liquid. Suggest how it could be heated safely - ANS Use a water bath
Explain how a chromatogram shows that different dyes are different from each other -
ANS Each dyes has a different mixture
State the expression for calculating molar concentration - ANS Molar concentration =
Amount (in moles)/volume (in dm^³)
Which cation gives a crimson red flame colour? - ANS Li⁺
Which cation gives a orange flame colour? - ANS Na⁺
Which cation gives a lilac flame colour? - ANS K⁺
Which cation gives a brick red flame colour? - ANS Ca²⁺
Describe how you would carry out a flame test - ANS Put solid onto a wire. Put into a blue
flame
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,How would you test for the ammonium ion? - ANS Add sodium hydroxide. If ammonium ions
were present, ammonia gas will form which will turn damp red litmus paper blue
Describe how you would test for Cu²⁺ ions - ANS Add sodium hydroxide and a blue
precipitate will form
Give the formula of the blue precipitate formed when sodium hydroxide is added to a solution
containing Cu²⁺ - ANS Cu(OH)₂
Describe how you would test for Fe²⁺ ions - ANS Add sodium hydroxide and a green
precipitate will form
Write a word equation for the reaction between sodium hydroxide and iron(II) sulfate -
ANS sodium hydroxide + iron(II) sulfate -> iron (II) hydroxide + sodium sulfate
Describe how you would test for Fe³⁺ ions - ANS Add sodium hydroxide and a brown
precipitate will form
What 2 things are added to a solution to test for chloride ions? What is observed if they are
present? - ANS Add dilute nitric acid and silver nitrate. A white precipitate of silver chloride is
formed.
Describe the test for bromide ions. - ANS Add dilute nitric acid and silver nitrate. A cream
precipitate of silver bromide is formed.
After adding nitric acid and silver nitrate to a solution containing iodide ions, what colour
precipitate is formed? - ANS A yellow precipitate (of silver iodide) is formed.
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, Why is hydrochloric acid added before barium chloride solution in testing for sulfate ions? -
ANS To remove carbonate ions
Describe how you would test for sulfate ions - ANS Add dilute HCl, followed by BaCl₂. A white
precipitate will form
Write an chemical equation for the reaction between barium chloride and lithium sulfate
(Li₂SO₄). Include state symbols. Also, what would you see? - ANS BaCl₂ (aq) + Li₂SO₄ (aq) ->
BaSO₄ (s)+ 2LiCl (aq). Observe a white precipitate of barium sulfate.
Describe how you would test for carbonate ions, CO₃²⁻ - ANS Add nitric acid and see if carbon
dioxide bubbles form
Describe the test for ammonia gas - ANS Turns damp red litmus paper blue
State the expression for calculating % yield. (Triple science only!) - ANS % yield = (actual
amount of products/theoretical amount of products) x100
Describe the chemical test for water - ANS Add water to anhydrous copper(II) sulfate which
will change from white to blue if water is present
What is the symbol for a reversible reaction? - ANS
The addition of water to anhydrous copper sulfate can be used to test for the presence of
water. The reaction is reversible. What is the word equation? Describe the colour change. -
ANS anhydrous copper sulfate (white) + water <-> hydrated copper sulfate (blue)
Ammonia and hydrogen chloride react together in a reversible reaction to produce a white
solid. What are the word and symbol equations? - ANS ammonia + hydrogen chloride <->
ammonium chloride NH₃ + HCl <-> NH₄Cl
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
QUESTIONS AND ANSWERS 100% PASS
State the method used to obtain sand from a mixture of sand and water - ANS filtration
State the method used to obtain solid copper sulfate from aqueous copper sulfate -
ANS crystallisation
State the method used to obtain red food dye from a mixture of food dyes - ANS paper
chromatography
State the method used to obtain water from salt water - ANS simple distillation
Draw a diagram to show equipment used in simple distillation - ANS For what process is this
equipment used?
State the method used to obtain kerosene from a crude oil. - ANS fractional distillation
Draw the equipment used in fractional distillation in the lab - ANS For what process is this
equipment used?
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,Explain how fractional distillation is used to separate a mixture of different liquids - ANS The
different liquids have different boiling points
State the method used to extract the red dye from a sample of rose petals - ANS dissolving
Describe how pure salt can be obtained from rock salt - ANS 1) Grind rock salt into a fine
powder. 2) Add powder to hot water and stir to dissolve salt. 3) Filter mixture. Salt solution
passes through the filter paper leaving behind the sand. 4) Boil filtrate to evaporate some of the
water. 5) Leave saturated solution to cool so that crystals of salt form. 6) Filter cold mixture to
separate the crystals from the remaining solution.
Ethanol is a flammable liquid. Suggest how it could be heated safely - ANS Use a water bath
Explain how a chromatogram shows that different dyes are different from each other -
ANS Each dyes has a different mixture
State the expression for calculating molar concentration - ANS Molar concentration =
Amount (in moles)/volume (in dm^³)
Which cation gives a crimson red flame colour? - ANS Li⁺
Which cation gives a orange flame colour? - ANS Na⁺
Which cation gives a lilac flame colour? - ANS K⁺
Which cation gives a brick red flame colour? - ANS Ca²⁺
Describe how you would carry out a flame test - ANS Put solid onto a wire. Put into a blue
flame
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,How would you test for the ammonium ion? - ANS Add sodium hydroxide. If ammonium ions
were present, ammonia gas will form which will turn damp red litmus paper blue
Describe how you would test for Cu²⁺ ions - ANS Add sodium hydroxide and a blue
precipitate will form
Give the formula of the blue precipitate formed when sodium hydroxide is added to a solution
containing Cu²⁺ - ANS Cu(OH)₂
Describe how you would test for Fe²⁺ ions - ANS Add sodium hydroxide and a green
precipitate will form
Write a word equation for the reaction between sodium hydroxide and iron(II) sulfate -
ANS sodium hydroxide + iron(II) sulfate -> iron (II) hydroxide + sodium sulfate
Describe how you would test for Fe³⁺ ions - ANS Add sodium hydroxide and a brown
precipitate will form
What 2 things are added to a solution to test for chloride ions? What is observed if they are
present? - ANS Add dilute nitric acid and silver nitrate. A white precipitate of silver chloride is
formed.
Describe the test for bromide ions. - ANS Add dilute nitric acid and silver nitrate. A cream
precipitate of silver bromide is formed.
After adding nitric acid and silver nitrate to a solution containing iodide ions, what colour
precipitate is formed? - ANS A yellow precipitate (of silver iodide) is formed.
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Why is hydrochloric acid added before barium chloride solution in testing for sulfate ions? -
ANS To remove carbonate ions
Describe how you would test for sulfate ions - ANS Add dilute HCl, followed by BaCl₂. A white
precipitate will form
Write an chemical equation for the reaction between barium chloride and lithium sulfate
(Li₂SO₄). Include state symbols. Also, what would you see? - ANS BaCl₂ (aq) + Li₂SO₄ (aq) ->
BaSO₄ (s)+ 2LiCl (aq). Observe a white precipitate of barium sulfate.
Describe how you would test for carbonate ions, CO₃²⁻ - ANS Add nitric acid and see if carbon
dioxide bubbles form
Describe the test for ammonia gas - ANS Turns damp red litmus paper blue
State the expression for calculating % yield. (Triple science only!) - ANS % yield = (actual
amount of products/theoretical amount of products) x100
Describe the chemical test for water - ANS Add water to anhydrous copper(II) sulfate which
will change from white to blue if water is present
What is the symbol for a reversible reaction? - ANS
The addition of water to anhydrous copper sulfate can be used to test for the presence of
water. The reaction is reversible. What is the word equation? Describe the colour change. -
ANS anhydrous copper sulfate (white) + water <-> hydrated copper sulfate (blue)
Ammonia and hydrogen chloride react together in a reversible reaction to produce a white
solid. What are the word and symbol equations? - ANS ammonia + hydrogen chloride <->
ammonium chloride NH₃ + HCl <-> NH₄Cl
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
