The Mole Concept: Mass Relationships

What is the mole (mol)?

The mole is the SI unit for “amount of a substance” and is a unit quantity which refers to how much of an element or compound is present.

We have used other words to represent an understood amount, such as “a couple” meaning 2 or “dozen” meaning 12. Consider the same for the mole. A mole can represent how much or amount of a substance.

Moles and Mass

1 mole of an element is 1 unit of that element:

  • 1 mole of carbon is the same as saying 1 unit of carbon or 1 C
  • 1 mole of carbon is equivalent to the atomic mass of carbon
  • 1 mole of carbon = 12 g of carbon

1 mole of a compound is equivalent to the formula weight of the compound:

  •  1 mole of glucose is the same as saying 1 unit of glucose or 1 C6H12O6.
  •  1 mole of a compound is equivalent to the formula weight of the compound
  •  1 mole of glucose = 180 grams

IMPORTANT NOTE: These equivalencies are conversion factors! You can use dimensional analysis to convert one unit to another like any other simple unit conversion.

mole grams conversion factor

Related Bytes: Dimensional analysis and calculating formula weight

Recall the set up of dimensional analysis such that given units are positioned to cancel out!

Let’s try some examples:

1. How many moles are in 144 grams of glucose, C6H12O6?

Glucose

2. How many grams of NaOH are present in 3.45 moles of NaOH? [Ans: 138]

NaOH

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