Nhận biết (M1)

While researching a topic, a student has taken the following notes:

• • Element abundance is a relative measure of the amount of a chemical element in a given environment.

• • Abundance can be expressed as a mass fraction.

• • A mass fraction is the ratio of the total mass of an element to the combined mass of all elements in a given environment.

• • The mass fraction of magnesium (Mg) on Earth is 154,000 parts per million (ppm).

• • The mass fraction of zinc (Zn) on Earth is 40 ppm.

The student wants to specify the total mass of Earth’s magnesium relative to that of all elements. Which choice most effectively uses relevant information from the notes to accomplish this goal?

• A.

  Magnesium’s abundance on Earth is greater than zinc’s, as reflected by magnesium’s higher mass fraction.

• B.

  Magnesium’s abundance can be expressed by a mass fraction, a measure of the element’s mass relative to that of all elements on Earth.

• C.

  The mass fraction of magnesium on Earth is 154,000 ppm.

• D.

  Magnesium’s mass relative to the combined mass of all elements on Earth is 40 ppm.