A LevelChemistryAQAExam Questions1. Physical Chemistry1.2 Formulae, Equations & Calculations

Formulae, Equations & Calculations (AQA A Level Chemistry)

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1.2 Formulae, Equations & Calculations

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1.2 Formulae, Equations & Calculations

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11 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

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21 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

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31 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%

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41 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

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    51 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

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    61 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

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    71 mark

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

    • fraction numerator A v e r a g e space m a s s space o f space o n e space a t o m over denominator 1 divided by 12 space m a s s space o f space a n space a t o m space o f space to the power of 12 C end fraction

    • 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

    • fraction numerator A v e r a g e space m a s s space o f space o n e space m o l e c u l e over denominator M a s s space o f space a n space a t o m space o f space to the power of 12 C end fraction

    • fraction numerator A v e r a g e space m a s s space o f space o n e space m o l e c u l e over denominator 1 divided by 12 space m a s s space o f space a n space a t o m space o f space to the power of 12 C end fraction

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    81 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

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    91 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

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    101 mark

    Which is the correct expression for the percentage atom economy?

    • begin mathsize 14px style fraction numerator Molecular space mass space of space the space desired space product space over denominator The space sum space of space the space molecular space masses space of space all space reactants end fraction cross times space 100 end style

    • begin mathsize 14px style fraction numerator Actual space yield space of space the space desired space product over denominator Theoretical space yield space of space the space desired space product space end fraction cross times space 100 end style

    • begin mathsize 14px style fraction numerator The space sum space of space the space molecular space masses space of space the space reactants over denominator Molecular space mass space of space the space desired space product end fraction cross times 100 end style

    • begin mathsize 14px style fraction numerator The space total space mass space of space the space element space in space the space compound over denominator The space total space mass space of space the space compound end fraction cross times space 100 end style

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    11 mark

    The skeletal formula of limonene is shown.

    qf1kQJGh_8

    What is the empirical formula of limonene?

    • C10H16

    • C5H8

    • C10H12

    • C5H6

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    21 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

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    31 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

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    41 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

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    51 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

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    61 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

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    71 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%

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    81 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%

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    91 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

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    101 mark

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

    The initial temperature was 19.0 degreeC and the final temperature was 26.5 degreeC.

    Each reading of the thermometer has an uncertainty of ± 0.5 degreeC.

    What is the percentage uncertainty in the temperature change?

    • 1.89%

    • 2.63%

    • 6.67%

    • 13.3%

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    11 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

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    21 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

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    31 mark

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

    • VO2

    • V2O5

    • V3O7

    • V4O7

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    41 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

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    51 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)

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    61 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

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    71 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

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    81 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

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    91 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

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      101 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

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