AP®ChemistryCollege BoardExam QuestionsUnit 1: Atomic Structure & PropertiesMass Spectra of Elements

Mass Spectra of Elements (College Board AP® Chemistry): Exam Questions

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Mass Spectra of Elements

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11 mark

An element consists of two isotopes 69X and 71X, whose abundances are 60% and 40% respectively. What is the relative atomic mass of element X?

  • 69.2

  • 69.8

  • 70.0

  • 70.2

Choose your answer

11 mark
mass spectrum for AP chemistry

The mass spectrum of element X is shown above? Which of the following is true?

  • Element X is germanium.

  • X has a relative atomic mass between 71 and 72.

  • The most abundant isotope of X contains a total of 71 protons and neutrons.

  • The spectrum shows the abundance of the isotope 72X is greater than the abundance of the 70X.

Choose your answer

21 mark

Element Z has three isotopes: 70Z, 72Z and 74Z. They occur naturally with abundances of 24.4%, 32.4% and 43.2%, respectively. What is the average atomic mass of element Z?

  • 72.38 amu

  • 72.00 amu

  • 72.22 amu

  • 72.16 amu

Choose your answer

31 mark

A sample of neon contains the isotopes 20Ne and 21Ne. The average 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%

Choose your answer

11 mark

Iron has many different naturally occurring isotopes.

  Isotope            

       % Abundance   

      Isotopic mass      

   54Fe

5.845

53.9396

   56Fe

91.754

55.9349

   57Fe

2.119

56.9354

   58Fe

0.282

57.9333

What is the average atomic mass of iron?

  • 56.1858 amu

  • 54.200 amu

  • 59.270 amu

  • 55.845 amu

Choose your answer

21 mark

m / z value

84

86

87

88

% abundance

0.56

To be found

To be found

82.58

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

Strontium has a relative atomic mass of 87.71. 

What percentage 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%

Choose your answer

31 mark
Mass spectrum graph showing percentage abundance on the y-axis and mass-to-charge ratio on the x-axis, with a prominent peak around 20 m/z.

The mass spectrum of a sample of element X is shown above.

There are four peaks at m / z = 12, 24, 25 and 26.

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

Choose your answer