IGCSE CHEM P4 REVISION

Column Alpha

100

Name the substance used to remove sulfur dioxide in flue gas desulfurisation.

calcium oxide

100

Methanoic acid is represented by the formula HCOOH.

Name this type of formula.

structural

200

State two reasons why carbon (graphite) is suitable to use as an electrode.

Inert

Good conductor of electricity

300

Amino acids are colourless.

A sample containing a mixture of amino acids is separated. Each amino acid is detected and identified.

a) Name the process used to separate the amino acids.

b) Name the type of substance used to detect the amino acids.

c) Give the symbol of the value used to determine the identity of each amino acid after separation and detection.

M1 chromatography (1)

M2 locating agent (1)

M3 R_f (1)

400

Describe the observations when potassium is added to cold water. Write a balanced equation for the reaction. Include state symbols.

any 2 observations from:

 solid moves / floats

 solid dissolves / disappears

 bubbles / effervescence / fizzes

 lilac flame

 explodes

 melts / forms a spherical shape

2K(s) + 2H₂O(l) →2KOH(aq) + H₂(g)

Column Beta

100

Lithium, sodium and potassium are Group I elements.

Name the type of bonding in these elements.

Metallic (bonding)

100

Name a halide compound which can be used to detect the presence of water.

anhydrous cobalt(II) chloride

200

Sodium hydrogensulfate, NaHSO₄, dissolves in water to produce an aqueous solution, X, containing Na⁺, H⁺ and SO₄^2– ions.

State the observations when copper(II) oxide is warmed with an excess of X.

blue solution(1)

solid dissolves / disappears(1)

300

Proteins are natural polymers. Proteins contain amide linkages.

Synthetic polyamides also contain amide linkages.

a) Name a synthetic polyamide.

b) Identify the two monomers used to produce synthetic polyamides.

a) nylon

b) dicarboxylic acid, diamine

400

Nitrogen reacts with hydrogen to form ammonia, NH₃, in the Haber process.

State the essential conditions in the Haber process. Write an equation for the chemical reaction.

450 °C (1)

200 atmospheres (1)

iron catalyst (1)

N₂ + 3H₂ ⇌ 2NH₃ (1)

Column Gamma

100

State the class of oxide to which copper(II) oxide belongs.

basic (oxide)

100

Name two forms of the element carbon which have giant covalent structures.

Graphite and diamond

200

Complete the chemical equation to show the formation of ethene from decane, C₁₀H₂₂.

C₁₀H₂₂ → C₄H₈ + ................... + ...................

→ C₂H₄ + C₄H₁₀ (2)

300

A metal spoon is electroplated with copper.

State what is used as:

a) the positive electrode (anode) 

b) the negative electrode (cathode) 

c) the electrolyte. 

a) copper

b) spoon

c) aqueous copper(II) sulfate / copper(II) nitrate

400

Alkali metals are reactive elements.

Identify the alkali metal which:

a) has the highest melting point

b) has the highest density

c) has the lowest reactivity

d) burns with a lilac flame

e) is found in fertilisers to improve plant growth.

lithium / Li 

francium / Fr 

lithium / Li

potassium / K

potassium / K

Column Delta

100

Explain why members of a homologous series have similar chemical properties.

same functional group

100

Suggest why universal indicator is not suitable for titration.

too many colour changes

200

Give two reasons why the electrolysis is carried out on aluminium oxide dissolved in molten cryolite instead of electrolysing molten aluminium oxide only.

M1 improves electrical conductivity of the electrolyte 

M2 lower operating temperature

300

Chlorine(I) oxide, Cl₂O, is a simple molecule with covalent bonds.

Explain, in terms of structure and bonding, why Cl₂O boils at a low temperature and does not thermally decompose into its constituent elements, Cl₂ and O₂.

M1 (forces of) attraction between molecules are broken (during boiling)

M2 covalent bonds (between Cl and O atoms) are broken (during thermal decomposition)

M3 weak attraction between molecules and strong covalent bonds

400

Ethene, C₂H₄, is the first member of a family of similar compounds which contains the alkene functional group.

a) State the term for a family of similar compounds which contain the same functional group.

b) Determine the difference in relative molecular mass between C₂H₄ and the next member in this family of similar compounds.

c) Write the symbol equation for the complete combustion of C₂H₄.

a) homologous series

b) 14

c) C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

Column Sigma

100

Ammonia reacts with an acid to form ammonium sulfate, (NH₄)₂SO₄.

State the formula of the acid used.

H₂SO₄

100

Chloroethene monomers can be converted into a polymer called poly(chloroethene).

State the type of polymerisation that produces poly(chloroethene) from chloroethene.

addition

200

Describe the test for an unsaturated hydrocarbon.

aqueous bromine (1)

turns colourless / decolourises (1)

300

(NH₄)₂Cr₂O₇ is a compound containing chromium.

The negative ion in (NH₄)₂Cr₂O₇ is Cr₂O₇^2–.

a) State the sum of the oxidation numbers in the Cr₂O₇^2– ion.

b) The oxidation number of each O in Cr₂O₇^2– ions is –2.

Determine the oxidation number of each Cr in Cr₂O₇^2– ions. Show your working.

a) -2

b) +6

400

Name the products and state the observations at the negative and positive electrodes when dilute aqueous potassium bromide, KBr, undergoes electrolysis.

product at negative electrode: hydrogen

observation at negative electrode: bubbles

products at positive electrode: oxygen and water

observation at positive electrode: bubbles