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Calculations Involving Masses (Edexcel GCSE Combined Science: Chemistry): Exam Questions

1 hour17 questions
Medium
Hard
11 mark

The diagram shows the displayed formula of succinic acid. 

2-1-displayed-formula-of-succinic-acid

What is the empirical formula for this compound?

  • C4H6O4

  • CH2O

  • C2H3O2

  • CHO

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2a4 marks

The apparatus in Figure 7 shows a piece of magnesium ribbon being heated.

fig-7-q6-1cho-1f-specimen-2018

Figure 7

During the heating, the magnesium reacts with oxygen from the air. The lid of the crucible was raised slightly from time to time. Magnesium oxide was formed as a white powder. The experiment was repeated with different masses of magnesium. The results are shown in Figure 8.

experiment

mass of magnesium used/g

mass of magnesium oxide formed/g

mass of oxygen in magnesium oxide/g

1

0.10

0.16

0.06

2

0.15

0.24

0.09

3

0.25

0.40

0.15

4

0.30

0.48

0.18

5

0.35

0.49

0.14

6

0.50

0.80

0.30

Figure 8

i) Draw a graph of the mass of oxygen in magnesium oxide against the mass of magnesium used.

fig--q6ai-1cho-1f-specimen-2018

(3)

ii) The result for experiment 5 is anomalous. The masses were all measured accurately.

Suggest a reason for this anomalous result.

(1)

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2b1 mark

Balance the equation for the reaction of magnesium with oxygen to form magnesium oxide.

....................... Mg + ....................... O2→ ........................ MgO

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2c
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Calcium nitrate contains calcium ions and nitrate ions.

Calculate the relative formula mass of calcium nitrate, Ca(NO3)2. (relative atomic masses: Ca = 40, N = 14, O = 16)

relative formula mass = .....................................................

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2d
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Two oxides of lead, R and S, were analysed.

The empirical formula of oxide R was found to be PbO.

The results of the analysis of oxide S showed it contained 0.207 g of lead combined with 0.032 g of oxygen.

Show, by calculation, that the two oxides had different empirical formulae. (relative atomic masses: O = 16, Pb = 207)

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3
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A company produces tin from an ore called cassiterite, which is mainly tin oxide.

What is the relative formula mass (Mr) of tin oxide, SnO2?

Relative atomic masses (Ar):   Sn= 119 O= 16

  • 135

  • 151

  • 270

  • 1904

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41 mark

Higher Only

Avogadro's constant has a value of 6.02 x 1023.

How many hydrogen atoms are in 0.05 moles of hydrogen molecules?

  • 3.01 x 1022

  • 3.01 x 1023

  • 6.02 x 1022

  • 6.02 x 1024

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5a1 mark

The molecular formula of butene is C4H8.

Which of the following is the empirical formula of butene?

  • CH

  • CH2

  • C4H8

  • (CH2)4

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5b2 marks

Calculate the relative formula mass of butene, C4H8.

(relative atomic masses: H = 1, C = 12)

relative formula mass ................................

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5c1 mark

When burnt completely in air, butene forms carbon dioxide and water.

i) Balance the equation for this reaction by putting numbers in the spaces provided.

C4H8 + 6O2 rightwards arrow ................ CO2 + ................ H2O

(2)

ii) Describe the test to show that a gas is carbon dioxide.

(2)

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5d1 mark

Substance X is a gas at room temperature. It is a simple molecular, covalent substance.

Which row of the table shows the properties that substance X is most likely to have?

 

boiling point
in °C

relative solubility
in water

square  A

–6

low

square  B

600

high

square  C

–6

high

square  D

600

low

    Choose your answer

    5e1 mark

    Diamond has a giant covalent structure.

    State one property of diamond that is the result of its giant covalent structure.

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    61 mark

    A piece of iron wool is left in moist air and goes rusty.

    Which graph shows how the mass of the iron wool changes?

    3-1-q-4-mass-changes

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      7
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      A student wanted to make 15.0 g of zinc chloride. The equation for the reaction is:

      ZnCO3 + 2HCl →  ZnCl2 + CO2 + H2O

      What mass of zinc carbonate should the student add to the hydrochloric acid to make 15.0 g of zinc chloride?

      Relative atomic masses (Ar): C = 12    Zn = 65   O= 16    Cl = 35.5     H= 1

      • 11.0 g

      • 13.8 g

      • 15.0 g

      • 22.0 g

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      81 mark

      Higher Only

      How many moles are present in 9 kg of glucose, C6H12O6?

      Relative formula mass (Mr):       C6H12O6 = 180

      • 0.02 mol

      • 0.05 mol

      • 20 mol

      • 50 mol

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      91 mark

      Higher Only

      What is the mass of 0.25 moles of hydrated copper(II) sulfate, CuSO4.5H2O?

      Relative formula mass (Mr):  H2O = 18  CuSO4 = 160

      • 40.0 g

      • 44.5 g

      • 62.5 g

      • 1000 g

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      101 mark

      Higher Only

      Nitrogen and hydrogen react together to make ammonia.

      N2 + 3H2  → 2NH3

      If 2.0 g of hydrogen is added to 12.0 g of nitrogen which substance is the limiting reactant and how much of the excess reactant remains?

      Relative atomic masses (Ar): H = 1    N = 14

       

      Limiting Reactant

      Mass of excess reactant

      A

      nitrogen

      2.0 g

      B

      nitrogen 

      10.0 g

      C

      hydrogen

      2.7 g

      D

      hydrogen

      9.3 g

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        111 mark

        A solution of CuSO4 has a concentration of 35 g dm-3.

        What mass of CuSO4 would there be in 250 cm3 of the solution?

        • 140 g

        • 8.75 g

        • 7.14 g

        • 1.40 g

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        121 mark

        What is the relative formula mass of butene, C4H8 ?

        (relative atomic masses: H=1, C=12)

        • 12

        • 13

        • 56

        • 100

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        1a5 marks

        Figure 13 shows a model of how particles are arranged in a solid.

        fig-13-q8-1cho-1h-specimen-2018

        Figure 13

         i) State two ways in which this model fails to accurately represent a crystal of sodium chloride.

        (2)

        ii) Magnesium oxide has a melting point of 2852 °C. Explain why magnesium oxide has such a high melting point.

        (3)

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        1b
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        i) Carbon dioxide can be formed by the reaction of calcium carbonate, CaCO3 with dilute hydrochloric acid.

        Write the balanced equation for this reaction.

        (3)

        ii) The thermal decomposition of copper carbonate forms copper oxide and carbon dioxide.

        CuCO3(s) → CuO(s) + CO2(g)

        15.0 g of pure copper carbonate is decomposed completely.

        Calculate the mass of solid produced.

        (relative atomic masses: C = 12.0; O = 16.0; Cu = 63.5)

        Give your answer to two significant figures.

        (2)

        mass of solid = ................................................................. g

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        1c3 marks

        Higher Only

        Magnesium reacts with water in the form of steam as shown in the equation.

        Mg + 2H2O → Mg(OH)2+ H2

        2.4 g of magnesium reacts with sufficient steam for a complete reaction to form 5.8 g of magnesium hydroxide and 0.2 g of hydrogen. Show, by calculation, that the law of conservation of mass applies to this reaction. (relative atomic masses: H = 1.0, O = 16, Mg = 24)

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        2
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        2.7 g aluminium reacts with 38.1 g of iodine, I2, to make 40.8 g aluminium iodide, AlI3.

        (Relative atomic masses:     Al = 27        I = 127

        Relative formula mass:      AlI3 = 408)

        What coefficients would balance the equation for the reaction?

        • 1 : 3 : 2

        • 2 : 1: 2

        • 2 : 3 : 2

        • 3 : 2 : 3

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        3a4 marks

        A student placed a piece of metal P in a test tube containing excess dilute sulfuric acid. The student repeated this with three other metals, Q, R and S. All the pieces of all four metals were the same size.

        i) The student recorded the observations until each metal had reacted with the acid for two minutes.

        The observations are shown in Figure 9.

        metal

        observations

        P

        bubbles produced very slowly some metal remained

        Q

        bubbles produced quickly no metal remained

        R

        bubbles produced slowly no metal remained

        S

        bubbles produced very quickly no metal remained

        Figure 9

        Use this information to put the four metals in order of reactivity from the least reactive to the most reactive.

        (2)

        least reactive

         

         

         

         

        most reactive

        ii) Complete the diagram below to show how the student could add to the apparatus to measure the volume of gas produced in the two minutes.

        (2)

        fig-q9aii-1cho-1h-paper-1-june-2018

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        3b
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        When iron reacts with copper sulfate solution, solid copper is formed.
        Two possible equations for this reaction are

        A    CuSO4 + Fe → Cu + FeSO4
        B    3CuSO4 + 2Fe →  3Cu + Fe2(SO4)3

        It was found that 10.00 g of iron powder reacted with excess copper sulfate solution to produce 11.34 g of copper.
        Carry out a calculation to decide which equation, A or B, represents the reaction taking place.

        (relative atomic masses: Fe = 56.0, Cu = 63.5)

        How did you do?

        3c2 marks

        Higher Only

        Acid solutions contain hydrogen ions.

        Aluminium reacts with dilute hydrochloric acid to form a solution containing aluminium ions, Al3+.

        Complete the balanced ionic equation for this reaction.

        ................... + .................. H+ rightwards arrow.................. AI3+ + ...................

        How did you do?

        3d1 mark

        Higher Only

        The hydrogen ion concentration in a solution is decreased by a factor of 10.

        State how the pH of this solution changes.

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        3e
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        Higher Only

        Calculate the mass, in g, of a hydrogen atom, using the data below.

        (relative atomic mass: H = 1.00;

        Avogadro constant = 6.02 × 1023)

        mass of hydrogen atom = ......................................g

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        4a1 mark

        Sodium hydroxide is added to sulfuric acid.

        Name the type of reaction that takes place.

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        4b1 mark

        Complete the balanced symbol equation for the reaction.

        2NaOH (aq) + H2SO4 (aq) → ………… (aq) + ………. (l)

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        4c4 marks

        Higher Tier Only

        Calculate the mass of sodium hydroxide needed to add to 1 dm3 of water to make solution with a concentration of 0.2 mol dm-3.

        Show your working out.

        (relative atomic masses: Na = 23, O = 16, H = 1)

        How did you do?

        4d4 marks

        Higher Tier Only

        Deduce which reactant is in excess when 100 cm3 of 0.2 mol dm-3 sodium hydroxide reacts completely with 50 cm3 of 0.5 mol dm-3 sulfuric acid.

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        5a2 marks

        A student reacted calcium carbonate with hydrochloric acid. They wanted to investigate how the mass changed during the reaction.

        Figure 1 shows the equipment they used.

        edx-1-6h-paper-1-q5a-calcium-carbonate-and-acid-reaction

        Figure 1

        Give the function of the cotton wool.

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        5b2 marks

        The symbol equation for the reaction is:

        CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O (l)

        Calculate the relative formula mass of calcium carbonate.

        (relative atomic masses: Ca = 40, C = 12, O = 16)

        How did you do?

        5c3 marks

        Higher Tier Only

        They used 0.25 mol of hydrochloric acid.

        Calculate the minimum mass of calcium carbonate that must be added to react with all the hydrochloric acid.

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        5d4 marks

        The student measures the mass of the contents of the flask at the start and end of the reaction.

        i) Describe one way they could tell the reaction was over.

        [1]

        ii) Explain why the results from this experiment do not appear to support the law of conservation of mass.

        [3]

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