plumiEmpirical and molecular formula: AQA A‑Level Chemistry questions
AQA A-Level Chemistry past-paper questions on 3.1.2.4 Empirical and molecular formula, 2008–2025, with mark schemes and examiner’s reports where available.
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Q03.4
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All 50 questions on Empirical and molecular formula, as a list
- June 2025, Paper 2, Q03.4 (4 marks): An incomplete equation for the reaction used to make DIBP is shown. Complete the equation. Give the name of the mechanism for this reaction. Deduce the empirica
- June 2024, Paper 2, Q07 (4 marks): Compound L (Mr = 88.0) contains carbon, hydrogen and oxygen only. A 6.56 × 10–4 mol sample of L burns completely in air to form 2.62 × 10–3 mol of water and 2.6
- June 2024, AS Paper 1, Q18 (1 mark): What is the empirical formula of an oxide of chlorine that contains 42.5% by mass of chlorine? [1 mark] A ClO2 B ClO3 C Cl2O3 D Cl2O5
- June 2024, AS Paper 2, Q01.2 (3 marks): 0.500 g of a hydrocarbon is analysed. The hydrocarbon contains 0.450 g of carbon. Calculate the empirical formula of this hydrocarbon. [3 marks] Empirical formu
- June 2023, Paper 2, Q08.4 (3 marks): A sample of a different biofuel, made from sewage sludge, is found to contain 37.08% carbon, 5.15% hydrogen and 24.72% oxygen by mass. The rest of the sample is
- June 2023, AS Paper 2, Q21 (1 mark): Which compound has the empirical formula C2H4O? [1 mark] A butanal B ethanoic acid C ethanol D methylpropanoic acid
- June 2022, Paper 3, Q02 (6 marks): Tschermigite is a hydrated, water-soluble mineral, with relative formula mass of 453.2 The formula of tschermigite can be represented as M.x H2O, where M repres
- June 2022, AS Paper 1, Q14 (1 mark): 5.0 g of an oxide contains 4.0 g of molybdenum. What is the empirical formula of this oxide? [1 mark] A MoO2 B MoO5 C Mo2O3 D Mo3O2
- June 2022, AS Paper 2, Q03.5 (4 marks): Several saturated halogenoalkanes contain 17.8% carbon, 3.0% hydrogen and 79.2% bromine by mass. Calculate the empirical formula of these compounds. Give the IU
- June 2022, AS Paper 2, Q17 (1 mark): Which compound has the same empirical formula and molecular formula? [1 mark] A butane B but-1-ene C propane D propene Questions 18, 19 and 20 Methanol is made
- November 2021, AS Paper 2, Q10 (1 mark): A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Which could be the molecular formula of this compound? [1 mark] A C2H2O2 B C2H2O C C2H
- November 2020, Paper 2, Q08.1 (5 marks): A 1.50 g sample of H3Y.𝑥𝑥H2O contains 0.913 g of oxygen by mass. The sample burns completely in air to form 1.89 g of CO2 and 0.643 g of H2O Show that the empir
- November 2020, Paper 2, Q08.2 (2 marks): A 3.00 g sample of H3Y.𝑥𝑥H2O (Mr = 210.0) is heated to constant mass. The anhydrous H3Y that remains has a mass of 2.74 g Show, using these data, that the value
- November 2020, AS Paper 2, Q16 (1 mark): What is the empirical formula of a hydrocarbon that contains 90% carbon by mass? [1 mark] A C2H3 B C3H2 C C3H4 D C4H3
- June 2019, Paper 2, Q03.1 (4 marks): Deduce the molecular formula of isoprene and suggest a possible structure. [4 marks] Molecular formula Structure
- June 2019, Paper 2, Q10.1 (3 marks): A dicarboxylic acid has a relative molecular mass of 118, to the nearest whole number. Deduce the molecular formula of the acid. [3 marks] Molecular formula
- June 2019, AS Paper 1, Q10 (1 mark): 5.0 g of an oxide of molybdenum contain 4.0 g of molybdenum. What is the empirical formula of this oxide? [1 mark] A MoO2 B Mo4O5 C Mo2O3 D Mo3O2
- June 2018, Paper 3, Q05 (1 mark): Which can be both an empirical and molecular formula of a stable compound? [1 mark] A CH2O B P4O10 C NH2 D CH3
- June 2018, AS Paper 1, Q03.1 (5 marks): Use the data in Table 1 to calculate a value for x in the formula Na2CO3. xH2O Give your answer to 2 decimal places. [5 marks] Value for x
- June 2018, AS Paper 1, Q03.2 (1 mark): The correct value for x is 10 Suggest a reason for the difference between the experimental value for x and the correct value. (If you were unable to calculate a
- June 2018, AS Paper 1, Q03.3 (2 marks): Suggest how the procedure could be improved, using the same apparatus, to give a more accurate value for x Justify your answer. [2 marks] Suggestion Justificati
- June 2018, AS Paper 2, Q05.1 (6 marks): A hydrocarbon contains 87.8% by mass of carbon and has a relative molecular mass (Mr) of 82.0 The hydrocarbon decolourises bromine water. Determine the empirica
- June 2017, AS Paper 1, Q22 (1 mark): 2 2 What is the empirical formula of an oxide of nitrogen that contains 26% nitrogen by mass? [1 mark] A NO2 B N2O3 C N2O5 D N4O5
- June 2017, AS Paper 2, Q02.2 (4 marks): Analysis of a different hydrocarbon Y shows that it contains 83.7% by mass of carbon. Calculate the empirical formula of Y. Use this empirical formula and the r
- June 2016, AS Paper 1, Q21 (1 mark): In a molecule of a hydrocarbon, the fraction by mass of carbon is 9 11 What is the empirical formula of the hydrocarbon? [1 mark A CH B CH3 C C3H8 D C5H12
- June 2016, AS Paper 2, Q14 (1 mark): An organic compound is found to contain 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. Which of the following compounds could this be? [1 mark] A Ethanol B Ethan
- Specimen, Paper 2, Q03.8 (3 marks): Isooctane reacts with an excess of chlorine to form a mixture of chlorinated compounds. One of these compounds contains 24.6% carbon and 2.56% hydrogen by mass.
- June 2016, CHEM4 (old spec), Q9(a) (3 marks): Use these data to show that the molecular formula of R is C6H14O2 [3 marks]
- June 2016, CHEM1 (old spec), Q3(b)(i) (1 mark): State what is meant by the term empirical formula. [1 mark]
- June 2016, CHEM1 (old spec), Q3(b)(ii) (3 marks): Calculate the empirical formula of this basic copper carbonate. Show your working. [3 marks]
- June 2015, CHEM1 (old spec), Q4(a) (4 marks): Calculate the value of the integer x. Show your working. [4 marks]
- June 2015, CHEM1 (old spec), Q4(b) (2 marks): Suggest how a student doing this experiment could check that all the water had been removed. [2 marks]
- June 2014, CHEM1 (old spec), Q6(c) (4 marks): Calcium dihydrogenphosphate can be represented by the formula Ca(H2PO4)x where x is an integer. A 9.76 g sample of calcium dihydrogenphosphate contains 0.17 g o
- June 2013, CHEM1 (old spec), Q3(d) (1 mark): Deduce the empirical formula of graphane. (1 mark)
- June 2013, CHEM1 (old spec), Q7(a) (3 marks): People who have a zinc deficiency can take hydrated zinc sulfate (ZnSO4.xH2O) as a dietary supplement. A student heated 4.38 g of hydrated zinc sulfate and obta
- January 2013, CHEM1 (old spec), Q3(d)(iii) (4 marks): One of these compounds of oxygen and fluorine has a relative molecular mass of 70.0 and contains 54.3% by mass of fluorine. Calculate the empirical formula and
- January 2013, CHEM2 (old spec), Q5(a)(i) (1 mark): Deduce the empirical formula of glucose. (1 mark)
- June 2012, CHEM1 (old spec), Q5(e) (4 marks): A different compound of boron and chlorine has a relative molecular mass of 163.6 and contains 13.2% of boron by mass. Calculate the molecular formula of this c
- January 2012, CHEM1 (old spec), Q5(d) (3 marks): Calcium nitride contains 81.1% by mass of the metal. Calculate the empirical formula of calcium nitride. Show your working.
- June 2011, CHEM1 (old spec), Q2(c) (3 marks): Hydrated calcium nitrate can be represented by the formula Ca(NO3)2.xH2O where x is an integer. A 6.04 g sample of Ca(NO3)2.xH2O contains 1.84 g of water of cry
- January 2011, CHEM1 (old spec), Q2(e) (3 marks): Indium forms a compound X with hydrogen and oxygen. Compound X contains 69.2% indium and 1.8% hydrogen by mass. Calculate the empirical formula of compound X.
- June 2010, CHEM1 (old spec), Q4(a) (3 marks): An oxide of nitrogen contains 25.9% by mass of nitrogen. Determine the empirical formula of this oxide.
- January 2010, CHEM1 (old spec), Q2(e) (3 marks): Glauber’s salt is a form of hydrated sodium sulfate that contains 44.1% by mass of sodium sulfate. Hydrated sodium sulfate can be represented by the formula Na2
- June 2009, CHEM1 (old spec), Q2(c) (3 marks): 2 (c) Concentrated nitric acid reacts with magnesium to form an oxide of nitrogen which contains 30.4% by mass of nitrogen. Calculate the empirical formula of t
- January 2009, CHM1 (2008 spec), Q2(e)(i) (1 mark): 2 (e) (i) State what is meant by the term empirical formula of a compound. (1 mark)
- January 2009, CHM1 (2008 spec), Q2(e)(ii) (1 mark): 2 (e) (ii) Deduce the empirical formula of ethyne. (1 mark)
- January 2009, CHM1 (2008 spec), Q2(f) (3 marks): 2 (f) Ethyne can be used to make compound B (Mr = 215.8) which contains 22.24% carbon, 3.71% hydrogen and 74.05% bromine, by mass. Calculate the empirical formu
- June 2008, CHM6W (2008 spec), Q22 (1 mark): 22 Hydrocarbons which contain 85.7% by mass of carbon include 1 2 3 4 H3C C C CH3 CH3 Directions summarised A B C D 1, 2 and 3 1 and 3 2 and 4 4 only only corre
- January 2008, CHM3W (2008 spec), Q2(d)(i) (1 mark): (i) State what is meant by the term empirical formula. (1 mark)
- January 2008, CHM3W (2008 spec), Q2(d)(ii) (1 mark): (ii) Give the empirical formula of buta-l,3-diene. (1 mark)
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