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

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

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Mass Spectra of Elements

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1
1 point

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

  • 69.2

  • 69.8

  • 70.0

  • 70.2

Choose your answer

1
1 point
Mass spectrum of element X: abundance against m/z with three peaks at 70, 71 and 72. The peak at 71 is tallest, 70 is next and 72 is shortest.

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

  • Element X is germanium.

  • X has an average 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

2
1 point

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

3
1 point

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%

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1
1 point

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

2
1 point

m / z value

84

86

87

88

% abundance

0.56

To be found

To be found

82.58

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

Strontium has an average atomic mass of 87.71 amu.

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

3
1 point
Mass spectrum of element X: percentage abundance against m/z from 0 to 50, with a tall peak at m/z 24 and two short peaks at m/z 25 and 26.

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

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

Which of the following statements is / are correct?

  1. The most abundant isotope of X has a total of 24 protons and neutrons.

  2. Element X has three naturally occurring isotopes.

  3. The average 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