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Verbal·Expression of Ideas·Rhetorical Synthesis

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

• The ratio of the total mass of an element to the combined mass of all elements in a given environment is called the mass fraction.
• The mass fraction of chromium (Cr) on Earth is 4,700 parts per million (ppm).
• This indicates that the relative abundance of chromium on Earth is 0.47%.
• The ratio of the total number of atoms of an element to the total number of all atoms in a given environment is called the mole fraction.
• The mole fraction of chromium on Earth is 2,300,000 parts per billion (ppb).
• This indicates that the relative abundance of chromium on Earth is 0.23%.

The student wants to emphasize a similarity between mass fraction and mole fraction. Which choice most effectively uses relevant information from the notes to accomplish this goal?

A

On Earth, the mass fraction of chromium is 4,700 ppm, or 0.47%, and the mole fraction is 2,300,000 ppb, or 0.23%.

B

While mass fraction is a measure of relative mass and mole fraction is a measure of relative atom count, both indicate the relative abundance of elements on Earth.

C

Both mass and mole fraction express the relative abundance of chromium on Earth as a ratio of the total mass of chromium to the combined mass of all atoms.

D

The mass fraction of chromium indicates its relative mass; in addition, the element’s mole fraction indicates the relative number of chromium atoms.