Stoichiometry — IGCSE Science - Combined (0653) questions by topic
Formula-writing and balancing equations from given ratios drive this topic: deducing the formula for calcium phosphate from known ionic formulae, completing a combustion word equation for methane, and identifying which listed equation is correctly balanced. Complete, state and identify lead the command words, and complete wants every missing formula filled in correctly, not just partially matched.
This set contains 8 real questions from 2023 to 2025 papers, worth 1 to 9 marks, so single formula-selection sits beside multi-part equation completion. Submitting each answer for instant marking is useful here, since a swapped subscript or an unbalanced atom count in a chemical equation is caught immediately rather than repeated in later questions.
May–June 2025, Paper 11
The unbalanced equation for the reaction between aqueous sodium hydroxide and dilute sulfuric acid is shown. wNaOH + xH2SO4 - yNa2SO4 + zH2O Which values of w, x, y and z balance…
Answer this question and get it marked →May–June 2025, Paper 12
The ratio of the atoms Na : C : O in sodium carbonate is 2 : 1 : 3. What is the formula of sodium carbonate? A Na2CO3 B Na2(CO)3 C 2NaCO3 D 2Na2(CO3)2
Answer this question and get it marked →Which equation is balanced? A 2CO + O2 - 2CO2 B Cu + O2 - CuO C 2Mg + 2HCl - MgCl2 + H2 D 2N2 + 3H2 - 2NH3
Answer this question and get it marked →May–June 2025, Paper 21
The formula of sodium phosphate is Na3PO4. The formula of calcium nitrate is Ca(NO3)2. Which row shows the formula for calcium phosphate and the formula for sodium nitrate?…
Answer this question and get it marked →May–June 2025, Paper 32
Hydrogen peroxide, H2O2, decomposes into water and oxygen when a catalyst is added. Balance the symbol equation for the reaction. ............H2O2 - ............H2O + O2
Answer this question and get it marked →May–June 2025, Paper 33
Scientists are investigating the use of iron as a fuel in cars. Iron reacts with oxygen, as shown in equation 1. This reaction releases energy. The iron oxide formed is converted…
Answer this question and get it marked →May–June 2023, Paper 32
Methane, CH4, is the main constituent of natural gas. Complete the word equation for the complete combustion of methane. methane + → + water
Answer this question and get it marked →May–June 2023, Paper 41
An iron nail is placed in a test-tube with air (Fig. 8.1). After one week, a layer of rust has formed. The equation for the reaction that forms rust is 4Fe + O2 → Fe2O3. Balance…
Answer this question and get it marked →Other IGCSE Science - Combined topics
- Practical skills (96)
- Motion, forces and energy (53)
- Electricity and magnetism (38)
- Waves (32)
- Human nutrition (23)
- Acids, bases and salts (22)
- Organisms and their environment (21)
- Organic chemistry (21)
- Reproduction (20)
- Thermal physics (20)
- Plant nutrition (19)
- The Periodic Table (18)