A LevelChemistryAQAExam QuestionsPhysical ChemistryFormulae, Equations & Calculations

Formulae, Equations & Calculations (AQA A Level Chemistry): Exam Questions

Exam code: 7405

4 hours46 questions

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Formulae, Equations & Calculations

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1
1 mark

Which is the correct definition of relative atomic mass?

  • the total mass of the subatomic particles in an atom

  • the mass of an atom compared to 1/12 the mass of a carbon-12 atom

  • the mass of an atom compared to the mass of a hydrogen-1 atom

  • the mass of a proton

Choose your answer

2
1 mark

What is the minimum volume of 0.5 mol dm-3 sulfuric acid needed to fully react with 2.43 g of magnesium powder?

Mg (s) + H2SO4 (aq) → MgSO4 (aq) + H2 (g)

  • 20 cm3

  • 50 cm3

  • 100 cm3

  • 200 cm3

Choose your answer

3
1 mark

When calcium carbonate is heated it decomposes according to the following equation

CaCO3 (s)  → CaO (s) +CO2 (g)

If 6.00 g of calcium carbonate is heated and produces 2.73 g of calcium oxide, what is the percentage yield of calcium oxide?

  • 81.25%

  • 81.18%

  • 123.19%

  • 123.08%

Choose your answer

4
1 mark

What are the correct smallest whole number coefficients to balance the chemical equation? 

__ Mg3N2 (s)  + __H2O (l) → __Mg(OH)2 (aq) + __NH3 (aq)

 

Mg3N2

H2O

Mg(OH)2

NH3

A

1

6

3

2

B

1

3

3

1

C

2

6

2

2

D

2

6

3

2

    Choose your answer

    5
    1 mark

    Hydrogen and chlorine react according to the following equation

                                              H2 (g)  + Cl2 (g) → 2HCl (g)

    When 1.5 moles of chlorine reacts with 2.0 moles of hydrogen, what will be the result?

    • 3.5 mol of HCl

    • 1.5 mol of HCl and 0.5 mol of H2

    • 2.0 mol of HCl and 0.5 mol of Cl2

    • 3.0 mol of HCl and 0.5 mol of H2

    Choose your answer

    6
    1 mark

    A compound has an empirical formula of C2H6O and a molar mass of 92.0. What is the molecular formula of this compound?

    • C2H6O

    • C4H12O2

    • C6H18O3

    • C8H24O4

    Choose your answer

    7
    1 mark

    Which is the correct definition of relative molecular mass, Mr?

    • Average mass of one atom1/12 mass of an atom of 12C

    • fraction numerator sum from blank to blank of space left parenthesis p e r c e n t a g e space i s o t o p e space a b u n d a n c e space cross times space i s o t o p e space m a s s space n u m b e r right parenthesis over denominator 100 end fraction

    • Average mass of one moleculeMass of an atom of 12C

    • Average mass of one molecule1/12 mass of an atom of 12C

    Choose your answer

    8
    1 mark

    What is the relative molecular mass, Mr, of succinic acid?

    9

    • 114 g mol-1

    • 116 g mol-1

    • 118 g mol-1

    • 120 g mol-1

    Choose your answer

    9
    1 mark

    A compound of copper and oxygen is shown to contain 88.8% copper and 11.2% oxygen by mass.

    What is the correct empirical formula of the compound?

    • CuO

    • CuO2

    • Cu2O

    • Cu2O2

    Choose your answer

    10
    1 mark

    Which is the correct expression for the percentage atom economy?

    • Molecular mass of the desired product The sum of the molecular masses of all reactants× 100

    • Actual yield of the desired productTheoretical yield of the desired product × 100

    • The sum of the molecular masses of the reactantsMolecular mass of the desired product×100

    • The total mass of the element in the compoundThe total mass of the compound× 100

    Choose your answer

    1
    1 mark

    The skeletal formula of limonene is shown.

    qf1kQJGh_8

    What is the empirical formula of limonene?

    • C10H16

    • C5H8

    • C10H12

    • C5H6

    Choose your answer

    2
    1 mark

    When heated magnesium carbonate, MgCO3, will decompose to a white solid and a gas, X.

    6.90 g of anhydrous magnesium carbonate is heated until no further reaction takes place.

    What is the mass of X produced?

    • 3.61 g

    • 7.20 g

    • 3.60 g

    • 1.80 g

    Choose your answer

    3
    1 mark

    2.12 g of a metal element reacts with 300 cm3 of oxygen at 298 K and 100 kPa, to form a metal oxide containing O2- ions.

    The gas constant R = 8.31 J K–1 mol–1.

    Identify the metal.

    • Magnesium

    • Calcium

    • Strontium

    • Barium

    Choose your answer

    4
    1 mark

    An additive in petrol is composed of lead, carbon and hydrogen only. The compound contains 64.11% lead and 29.7% carbon by mass.

    What is the empirical formula of the additive?

    • PbC2H5

    • PbC8H20

    • Pb2C8H20

    • Pb2C16H40

    Choose your answer

    5
    1 mark

    A student completes a titration experiment to determine the percentage by mass of iron in steel wire.

    Their titration results are shown in the table.

     

    Rough

    1

    2

    3

    Initial volume / cm3 

    0.00

    0.15

    11.95

    7.00

    Final volume / cm3 

    24.35

    24.60

    36.70

    33.50

    Titre / cm3 

    24.35

    24.25

    24.55

    24.30

    Calculate the mean titre.

    • 24.36 cm3

    • 24.30 cm3

    • 24.28 cm3

    • 24.37 cm3

    Choose your answer

    6
    1 mark

    15.0 g of a compound contains 6.105 g of carbon, 0.765 g of hydrogen and 8.130 g of oxygen. The relative molecular mass of the compound is 118.0 g mol-1.

    What is the molecular formula of the compound?

    • C2H3O2

    • C4H8O4

    • CH1.5O

    • C4H6O4

    Choose your answer

    7
    1 mark

    Calcium carbonate undergoes thermal decomposition according to the following equation

    CaCO3 (s)  → CaO (s) + CO2 (g)

    If 6.00 g of calcium carbonate is heated and produces 2.73 g of calcium oxide, what is the percentage yield of calcium oxide?

    • 81.2%

    • 74.7%

    • 68.2%

    • 55.2%

    Choose your answer

    8
    1 mark

    The anti-cancer drug cisplatin has the chemical name dichlorodiamineplatinum (II). It is produced from a multi-step reaction. The first step in this reaction is shown in the following equation.

    KPtCl4 + 4KI → KPtI4 + 4KCl

    What is the percentage atom economy for the formation of the potassium tetraiodoplatinate (II), KPtI4, in this reaction?

    • 93.2%

    • 71.3%

    • 68.7%

    • 31.8%

    Choose your answer

    9
    1 mark

    A 13.81 g sample of magnesium sulphate, MgSO4.xH2O, was heated until no further change in mass was recorded. 6.75 g of the solid remained after strong heating.

    What is the value of x?

    • 2

    • 5

    • 6

    • 7

    Choose your answer

    10
    1 mark

    A thermometer was used to measure the temperature change in a calorimetry experiment. 

    The initial temperature was 19.0 °C and the final temperature was 26.5 °C.

    Each reading of the thermometer has an uncertainty of ± 0.5 °C.

    What is the percentage uncertainty in the temperature change?

    • 1.89%

    • 2.63%

    • 6.67%

    • 13.3%

    Choose your answer

    1
    1 mark

    What is the whole number coefficient for oxygen when the equation for the combustion of pentanol is balanced?

    C5H11OH (g)  +  O2 (g)  →  CO2 (g)  +  H2O (g)

    • 7

    • 8

    • 15

    • 16

    Choose your answer

    2
    1 mark

    A student reacted copper metal with excess sulfuric acid and collected 35.9 g of the hydrated copper sulfate crystals, CuSO4●5H2O crystals. The yield of crystals was 80.0%.

    What was the original mass of copper used?

    • 7.3 g

    • 9.1 g

    • 11.4 g

    • 17.9 g

    Choose your answer

    3
    1 mark

    What is the empirical formula of an oxide of vanadium that contains 57.7% vanadium by mass?

    • VO2

    • V2O5

    • V3O7

    • V4O7

    Choose your answer

    4
    1 mark

    Magnesium sulfate can be made by the reaction of magnesium oxide with sulfuric acid

    MgO + H2SO4 → MgSO4 + H2O

    1.96 g of magnesium sulfate was produced in a reaction which had a percentage yield of 87.5%.

    What mass of magnesium oxide, in mg, was used in the reaction?

    • 747

    • 750

    • 1247

    • 1.247

    Choose your answer

    5
    1 mark

    Which reaction has the highest atom economy for the production of the carbon containing product?

    • HCOOH (aq) + NH3 (aq) → HCONH2 (s) + H2O (l)

    • CH4 (g) + 2O2 (g) → 2H2O (g) + CO2 (g)

    • CH4 (g) + H2O (g) → 3H2 (g) + CO (g)

    • C (s) + 2H2O (g) → CO2 (g) + 2H2 (g)

    Choose your answer

    6
    1 mark

    4.900 g of a carbohydrate contains 2.063 g of carbon. The carbohydrate also contains 6.43% hydrogen by mass and the remainder of the carbohydrate is oxygen.

    The relative molecular mass of the carbohydrate is 342 g mol-1.

    What is the molecular formula of the carbohydrate?

    • CH2O

    • C10H30O12

    • C11H18O12

    • C12H22O11

    Choose your answer

    7
    1 mark

    A 250 cm3 solution was made by dissolving 3.56 g of Na2CO3●nH2O in pure water.

    26.70 cm3 of 0.150 mol dm-3 hydrochloric acid were required to neutralise a 25.0 cm3 of the solution.

    What is the value of n in the Na2CO3●nH2O?

    • 2

    • 4

    • 5

    • 7

    Choose your answer

    8
    1 mark

    In a thermal decomposition reaction, 6.27 g of calcium oxide is produced from calcium carbonate. The percentage conversion of calcium carbonate is 84.2%.

    What mass of calcium carbonate underwent thermal decomposition? 

    • 9.0 g

    • 9.4 g

    • 11.2 g

    • 13.3 g

    Choose your answer

    9
    1 mark

    Aspirin is a common analgesic used for the relief of aches and pains.

    13

    Which row correctly describes aspirin?

     

    Empirical formula

    Molecular formula

    Mr / g mol-1

    A

    C2H2O

    C9H8O4 

    180.0

    B

    C3H3O

    C9H12O4 

    184.0

    C

    C9H12O4 

    C9H12O4 

    184.0

    D

    C9H8O4 

    C9H8O4 

    180.0

      Choose your answer

      10
      1 mark

      Refer to the unbalanced equation below when answering this question.

      2KMnO4 + 5H2C2O4 + _HCl → 2MnCl2 + _H2O + 10CO2 + 2KCl

      In the balanced equation, the simplest mole ratio for hydrochloric acid to water is

      • 4 : 5

      • 3 : 4

      • 2 : 5

      • 1 : 2

      Choose your answer