SAT Subject Test Chemistry

PART 2

REVIEW OF MAJOR TOPICS

CHAPTER 6

Stoichiometry (Chemical Calculations) and the Mole Concept

MOLE RELATIONSHIPS

Because the mole is used often in chemistry to quantify the number of atoms, molecules, and several other items, it is important to know the relationships that exist and how to move from one to another. The following summarizes a number of these relationships:

TIP

Know how to use these mole relationships. They will be needed to do stoichiometry problems.

When dealing with elements—

Moles of an element × molar mass (atomic) = mass of the element

Mass of an element/molar mass (atomic) = moles of the element

When dealing with compounds—

Moles of a compound × molar mass (molecular) = mass of the compound

Mass of a compound/molar mass (molecular) = moles of the compound

When dealing with the molecules of a compound—

Moles of molecules × 6.02 × 10²³ = number of molecules

Number of molecules/6.02 × 10²³ = moles of molecules

When dealing with the atoms of elements—

Moles of atoms × 6.02 × 10²³ = number of atoms

Number of atoms/6.02 × 10²³ = moles of atoms