A LevelChemistryOCRExam Questions2. Foundations in Chemistry2.1 Atoms & Reactions

Atoms & Reactions (OCR A Level Chemistry)

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2.1 Atoms & Reactions

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2.1 Atoms & Reactions

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1
Sme Calculator1 mark

Which ion has a different number of electrons from the other three ions?

  • Ga3+

  • Cl−

  • S2-

  • Ca2+

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21 mark

The electron configuration of element X is: 1s22s22p63s23p4.

What is the formula of a compound formed when sodium reacts with element X?

  • NaX

  • NaX2

  • Na2X

  • Na2X3

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31 mark

In the Periodic Table, element X is in Group 2 and element Y is in Group 15 (5).

What is the likely formula of an ionic compound of X and Y?

  • X2Y5

  • X2Y3

  • X3Y2

  • X5Y2

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4
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Which row shows the atomic structure of 37Cl –?

  protons   neutrons electrons
A 17  18  20
B 17 20 18
C 18 19 17
D 20 17 21

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    51 mark

    What is the formula of ammonium sulfide?

    • NH4S

    • NH4SO4

    • (NH4)2S

    • (NH4)2SO4

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    6
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    How many electrons are in a 24Mg2+ ion?

    • 10

    • 12

    • 14

    • 22

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    71 mark

    What is the formula of chromium(III) sulfate?

    • Cr3SO4

    • Cr(SO4)3

    • Cr2(SO4)3

    • Cr3SO3

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    8
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    Which row shows the atomic structure of 55Mn2+?

      Protons  Neutrons Electrons
    A. 25 30 23
    B. 25 55 23
    C. 27 30 25
    D. 30 25 28

     

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      91 mark

      What is the correct working to calculate the relative atomic mass, Ar, of iridium?

       m/z value

      191

      193

       Relative abundance (%)

      62.7

      37.3

      • fraction numerator left parenthesis 191 space cross times space 193 right parenthesis space plus space left parenthesis 62.7 space cross times space 37.3 right parenthesis over denominator 100 end fraction

      • fraction numerator left parenthesis 191 space cross times space space 37.3 right parenthesis space plus space left parenthesis 193 cross times space 62.7 right parenthesis space over denominator 100 end fraction

      • (191 × 62.7) + (193 × 37.3)

      • fraction numerator left parenthesis 191 space cross times space 62.7 right parenthesis space plus left parenthesis 193 space cross times space 37.3 right parenthesis over denominator 100 end fraction

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      101 mark

      Which of the following statements about isotopes is not correct?

      • The carbon-14 isotope contains 2 more neutrons than the carbon-12 isotope

      • In a silicon-30 isotope, there are 14 protons

      • Isotopes contain different numbers of protons

      • In a magnesium-26 isotope there are 14 neutrons

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      1
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      Which of the following species has numbers of protons, neutrons and electrons that are all different?

      • straight F presubscript 9 presuperscript 19 superscript minus

      • Na presubscript 11 presuperscript 23 superscript plus

      • straight O presubscript 8 presuperscript 16 superscript minus

      • straight S presubscript 16 presuperscript 32 superscript 2 minus end superscript

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      2
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      An isotope of element X contains the same number of neutrons as are found in an atom of 53Mn. The isotope of X also contains 23 protons.

      Which is the correct symbol for isotope X?

      • X presubscript 28 presuperscript 51

      • straight V presubscript 23 presuperscript 51

      • straight X presubscript 23 presuperscript 28

      • straight X presubscript 23 presuperscript 51

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      3
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      A sample of neon contains the isotopes 20Ne and 21Ne.

      The relative atomic mass of the neon sample is 20.2.

      What is the percentage of 21Ne atoms in the sample of neon?

      • 8.0%

      • 20%

      • 80%

      • 92%

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      4
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      A sample of metal Z was analysed by mass spectrometry. The relative abundance of each isotope in a mass spectrum of the sample is shown.

      m/z value

      70

      72

      74

      Relative abundance (%)

      24.4

      32.4

      43.2

      What is the relative atomic mass of metal Z to 3 significant figures?

      • 72.33

      • 72.4

      • 72.45

      • 72.2

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      51 mark

      The mass spectrum of element A is shown below.

      ocr-2-1m-q5

      Which of the following statements is/are correct?

      1. Element A is germanium
      2. The most abundant isotope of A contains a total of 71 protons and neutrons
      3. A has a relative atomic mass between 70 and 71

      • 1, 2 and 3

      • Only 1 and 2

      • Only 2 and 3

      • Only 1

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      61 mark

      What is the correct formula of iron(III) nitrate?

      • Fe3NO

      • Fe3NO3

      • FeNO3

      • Fe(NO3)3

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      71 mark

      The unbalanced equation for the reaction of zinc with concentrated nitric acid is shown below.

      .........Zn + .........HNO3 → .........Zn(NO3)2 + .........NO2 + .........H2O

      What is the number of moles of HNO3 that react with 1 mole of Zn?

      • 2

      • 3

      • 4

      • 5

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      8
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      Which atom is not an isotope of bromine?

        Number of neutrons Mass number
      A 37 72
      B 39 73
      C 41 76
      D 43 78

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        91 mark

        Bromide ions, Br− (aq), react with MnO4− (aq). The unbalanced equation is shown below.

        Br− (aq) + MnO4− (aq) + H2O (l) → BrO3− (aq) + MnO2 (s) + OH− (aq)

        What is the ratio of MnO2 (s) to OH− (aq) in the balanced equation?

        • 1 : 1

        • 1 : 2 

        • 1 : 3

        • 2 : 3

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        10
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        Which is the correct number of subatomic particles for a phosphide ion?

          Protons Neutrons Electrons  
        A 15 16 18  
        B 16 15 16  
        C 16 15 18  
        D 15 15 15  

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          11 mark

          A sample of strontium was analysed by mass spectroscopy. Some of the relative abundances of each isotope are shown below.

          Strontium has a relative atomic mass of 87.71.

          m / z value

          84

          86

          87

          88

          % abundance

          0.56

          To be found

          To be found

          82.58

           

          Which % abundance values below are correct for strontium-86 and strontium-87 respectively?

          • 6.86% and 9.86%

          • 9.90% and 6.96%

          • 7.00% and 9.54%

          • 8.67% and 8.19%

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          21 mark

          Which sequence shows the correct order in which ions are deflected in mass spectrometry?

          • 2311Na+ > 2412Mg+ > 2412Mg2+

          • 2412Mg2+ > 2311Na+ > 2412Mg+

          • 2412Mg2+ > 2412Mg+ > 2311Na+

          • 2412Mg+ > 2311Na+ > 2412Mg2+

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          31 mark

          An acid and a base are the reactants in a neutralisation reaction.

          Which equation is correct for this reaction?

          • H2SO4 (aq) + NH3 (aq) → NH4SO4 (aq)

          • 2HNO3 (aq) + CaCO3 (aq) → Ca(NO3)2 (aq) +2H2O (l)

          • CH3COOH (aq) + NaOH (aq) → CH3COONa (aq) + H2 (g)

          • 2H3PO4 (aq) + 3K2O(s) → 2K3PO4 (aq) + 3H2O (l) 

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          41 mark

          Three ions of different elements are shown below.

          3717Cl-          3115P3-         3719K+

          Which of the following statements is/are correct?

          1. All three ions have the same number of electrons
          2. None of the ions have the same number of neutrons as each other
          3. Cl- and K+ have the same total number of subatomic particles

          • 1, 2 and 3

          • Only 1 and 2

          • Only 2 and 3

          • Only 1

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          51 mark

          The mass spectrum of a sample of element X is shown below. There are four peaks at m / z = 12, 24, 25 and 26.

          ocr-as-2-1h-mcq-q5-magnesium-mass-spectrum

          Which of the following statements is / are correct?

          1. The peak at m / z = 12 is due to a 24X2+ ion
          2. The peak at m / z = 12 is due to an ion with a total of 12 neutrons and protons
          3. The relative atomic mass of element X will be between 12 and 24

          • 1, 2 and 3

          • Only 1 and 2

          • Only 2 and 3

          • Only 1

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