IGCSE Chemistry (0971) — May–June 2025, Paper 21
40 questions · every question answerable online with instant point-by-point AI marking against the official mark scheme.
Start with Question 1 →A gas is placed in a sealed container with a fixed volume. The gas is heated. Which statements are correct? 1 The gas molecules move around faster. 2 The gas particles collide…
Answer this question and get it marked →A sample of ethanol is heated at a constant rate. The heating curve for this sample is shown. The curve plots temperature (y-axis) against time (x-axis) with six labelled points:…
Answer this question and get it marked →Which atom has an equal number of protons, neutrons and electrons? A 40-Ar (argon-40) B 1-H (hydrogen-1) C 23-Na (sodium-23) D 14-N (nitrogen-14)
Answer this question and get it marked →The only naturally occurring isotopes in a sample of europium are 151-Eu and 153-Eu. This sample of europium has a relative atomic mass, Ar, of 152. What is the percentage of…
Answer this question and get it marked →Which statement about potassium chloride is correct? A It has a high melting point because it is a giant structure with strong covalent bonds. B It conducts electricity when solid…
Answer this question and get it marked →Which dot-and-cross diagram shows the outer shell electron arrangement in a molecule of nitrogen? Each option shows two overlapping circles labelled N (the two nitrogen atoms),…
Answer this question and get it marked →Which statement about silicon(IV) oxide is correct? A It contains silicon ions and oxide ions arranged in a giant lattice. B It is used in electrical circuits because it can…
Answer this question and get it marked →Three organic molecules are described. - The molecular formula of propanoic acid is CH3CH2COOH. - The molecular formula of lactic acid is CH3CH(OH)COOH. - A glucose molecule…
Answer this question and get it marked →Calcium carbonate reacts with dilute hydrochloric acid. The equation for the reaction is shown. CaCO3 + 2HCl - CaCl2 + H2O + CO2 1.00 g of calcium carbonate is added to 50.0 cm^3…
Answer this question and get it marked →The diagram shows the electroplating of a steel object. A power supply has its positive (+) terminal connected to a copper electrode and its negative (-) terminal connected to the…
Answer this question and get it marked →Concentrated aqueous sodium chloride is electrolysed using inert electrodes. Which equation shows the correct ionic half-equation for the reaction at the anode? A Cl^- + e^- - Cl…
Answer this question and get it marked →Which equation represents the overall reaction in a hydrogen-oxygen fuel cell? A 2H2 + O2 - 2H2O B 2H2O - 2H2 + O2 C H2 + O2 - H2O2 D H2O2 - H2 + O2
Answer this question and get it marked →Water is added to anhydrous copper(II) sulfate in a test-tube. The mixture becomes hot. Which type of reaction and reaction pathway diagram apply to this reaction? Each option…
Answer this question and get it marked →The equation represents the reaction between ethanoic acid and ethanol. CH3COOH + CH3CH2OH <= CH3COOCH2CH3 + H2O Which type of reaction does this show? A addition B neutralisation…
Answer this question and get it marked →The graph shows the results of adding excess calcium carbonate to hydrochloric acid at 50 C and at 30 C. Only the temperature is changed. The graph plots total volume of carbon…
Answer this question and get it marked →Industrially, ammonia is made by the Haber process. The equation is shown. N2(g) + 3H2(g) <= 2NH3(g) deltaH = -92 kJ/mol The conditions used are 450 C and 200 atm. Which…
Answer this question and get it marked →Ethanol is warmed with acidified aqueous potassium manganate(VII). Which row describes the type of reaction of the ethanol and the colour change observed in the reaction mixture?…
Answer this question and get it marked →Two experiments involving acids R or S are done. - 0.10 mol of acid R completely dissolves in 500 cm^3 of water. 0.0048 mol of acid R is dissociated in the solution. - 0.10 mol of…
Answer this question and get it marked →Lead(II) sulfate is an insoluble salt. Which process is not used to prepare a pure sample of this salt? A crystallisation B drying C filtration D precipitation
Answer this question and get it marked →The formulae of two hydrated salts are shown. - CuSO4.xH2O - CoCl2.yH2O What are the values of x and y? The options give x and y: A x = 5, y = 5 B x = 5, y = 6 C x = 6, y = 5 D x…
Answer this question and get it marked →The properties of the elements change from left to right across the Periodic Table. Which statement describes how the properties change across Period 3? A Elements change from…
Answer this question and get it marked →Which property decreases down Group VII of the Periodic Table, from chlorine to iodine? A atomic number B density C reactivity D melting point
Answer this question and get it marked →Some properties of elements are listed. 1 They have good electrical conductivity. 2 They have high melting points. 3 They are malleable. 4 They have ions with variable oxidation…
Answer this question and get it marked →Two statements about noble gases are listed. 1 Noble gases are reactive, monatomic gases. 2 Noble gases all have a full outer shell of electrons. Which statements about noble…
Answer this question and get it marked →Which statement about the properties and uses of copper is correct? A It is used in electrical wiring, and it is ductile. B It is mixed with tin to make the alloy brass. C It is…
Answer this question and get it marked →Three statements about solid Z are listed. - It reacts with dilute hydrochloric acid to produce hydrogen. - It reacts very slowly with cold water and quickly with steam. - It is a…
Answer this question and get it marked →Four metals J, K, L and M are added separately to aqueous solutions of their ions. The results are shown in the table (tick = reaction, cross = no reaction). Columns are the…
Answer this question and get it marked →Which process is used in the extraction of iron from hematite? A electrolysis B precipitation C reduction D fractional distillation
Answer this question and get it marked →Galvanising prevents iron from rusting. Which statements about galvanising are correct? 1 Galvanising involves coating the iron with silver. 2 Galvanising prevents oxygen and…
Answer this question and get it marked →Nitrogen, phosphorus and potassium are essential elements for improved plant growth. Which mixture provides all three essential elements? The options give a mixture and its…
Answer this question and get it marked →Which statements help explain why an increasing amount of carbon dioxide or methane in the atmosphere causes global warming? 1 Carbon dioxide absorbs thermal energy from the…
Answer this question and get it marked →The exhaust gases from cars contain oxides of nitrogen. How are these oxides of nitrogen formed? A Nitrogen and oxygen from the air react together at the high temperatures in the…
Answer this question and get it marked →The structural formula of methyl ethanoate is CH3COOCH3. Which compounds are structural isomers of methyl ethanoate? 1 HCOOCH2CH3 2 CH3CH2COOH 3 HOCH2CH2CH2OH A 1, 2 and 3 B 1 and…
Answer this question and get it marked →What is the total number of covalent bonds in one molecule of propane? A 8 B 9 C 10 D 11
Answer this question and get it marked →Industrially, ethanol is produced by fermentation or by the reaction of ethene with steam. Which row is correct? The options compare fermentation with ethene + steam: A…
Answer this question and get it marked →Some properties of an organic compound, J, are listed. - It is a liquid at room temperature. - It is soluble in water. - A solution of J reacts with calcium carbonate to form…
Answer this question and get it marked →The structures of two monomers that are used to make a condensation polymer are shown. The first monomer is a dicarboxylic acid: HOOC-COOH (two C=O carbons each bonded to an -OH…
Answer this question and get it marked →Which item of apparatus is used to measure 25.0 cm^3 of aqueous sodium hydroxide? Each option shows a piece of laboratory glassware. A a teat pipette (dropping pipette). B a…
Answer this question and get it marked →Which method is used to obtain copper(II) sulfate crystals from an aqueous solution of copper(II) sulfate? A chromatography B condensation C evaporation D filtration
Answer this question and get it marked →A mixture of four different colourless amino acids is analysed by paper chromatography. The final chromatogram is shown: a strip of chromatography paper with a baseline near the…
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