Stoichiometry — IGCSE Chemistry (0971) questions by topic
Stoichiometry questions test formula and mass calculations: identifying the correct formula for a named compound such as sodium carbonate, working with masses of compounds evaporated from sea water, calculating how much oxygen reacts exactly with a given mass of magnesium, and explaining why a fixed mass of product forms regardless of excess reactant added. Calculate dominates the numerical work, while identify, state, describe and complete cover formula recognition and short written reasoning.
11 questions from 2025 papers sit here, worth between 1 and 12 marks. Because calculate answers depend on correct mole ratios from a balanced equation, submitting working for instant marking catches a wrong ratio or an arithmetic slip immediately, rather than that single error carrying through to an incorrect final mass or volume that looks reasonable at a glance.
May–June 2025, Paper 11
Which row shows the correct formula for the named substance? substance formula A cobalt(II) chloride Cu2Cl B sodium carbonate Na2CO3 C xenon Xe2 D ammonium sulfate NH4SO4
Answer this question and get it marked →The equation shows the thermal decomposition of magnesium carbonate. MgCO3 → MgO + CO2 [Mr: MgCO3, 84] Which mass of magnesium oxide is formed when 21.0 g of magnesium carbonate…
Answer this question and get it marked →May–June 2025, Paper 12
In the molecules CH4, HCl and H2O, which atoms use all of their outer shell electrons in bonding? A C and Cl B C and H C Cl and H D H and O
Answer this question and get it marked →The equation for the reaction of magnesium with oxygen is shown. 2Mg + O2 - 2MgO Which mass of oxygen reacts exactly with 6 g of magnesium? A 2 g B 4 g C 8 g D 16 g
Answer this question and get it marked →May–June 2025, Paper 21
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 →May–June 2025, Paper 22
A sample of element Q has two isotopes. Their relative masses and abundances are shown. relative mass of isotope abundance /% --- --- 238 66 244 34 What is the relative atomic…
Answer this question and get it marked →When 65 g of zinc reacts with 32 g of sulfur, 97 g of zinc sulfide is produced. When 65 g of zinc reacts with 40 g of sulfur, the mass of zinc sulfide produced is still 97 g.…
Answer this question and get it marked →Aluminium reacts with iron(III) oxide to form aluminium oxide and iron. Which chemical equation for the reaction between aluminium and iron(III) oxide is correct? A Al + FeO - AlO…
Answer this question and get it marked →The concentration of a solution of aqueous sodium hydroxide is 0.50 mol/dm^3. Which mass of sodium hydroxide is used to make 500 cm^3 of this solution? A 10 g B 20 g C 40 g D 160 g
Answer this question and get it marked →May–June 2025, Paper 31
This question is about sea water and the substances found in sea water. Table 2.1 shows the masses of the compounds formed when 1000 cm^3 of sea water is evaporated. Table 2.1…
Answer this question and get it marked →Other IGCSE Chemistry topics
- Organic chemistry (31)
- The Periodic Table (29)
- Metals (23)
- Experimental techniques and chemical analysis (19)
- Chemical reactions (14)
- Acids, bases and salts (14)
- Chemical bonding (11)
- Chemistry of the environment (10)
- States of matter (9)
- Electrochemistry (9)
- Atoms, elements and compounds (8)
- Chemical energetics (8)