The Mole Concept:
      This is a biology mole, NOT a chemistry mole.

Read the essay by Amedeo Avogadro (1811) W on a manner of determining the relative masses of the elementary molecules.

  A Mole Is:

  • 6.02 x 1023 of anything.
  • The formula mass in grams of a substance contains one mole of particles.
  • Na = AvogadroŽs Number = 6.02 x 1023

The mole is important because:
  • It allows us to weigh atoms in the lab.
  • It allows us to compare amounts of atoms in chemical reactions.
 

Basic mole calculations: convert mass to moles, and moles to molecules or atoms.

The following equalities are used in mole calculations:
1 mole = 6.02 x 1023 atoms or molecules = formula mass in grams
 

Examples of Mole Conversion Problems:

These problems are set up correctly using Factor Label. Use a calculator to find each answer with the proper number of significant digits.

  1. Given 12.011 grams of carbon, how many atoms do you have?

    answer = 6.02 23 atoms

  2. Given 18 grams of water, how many molecules do you have?

    answer = 6.0 23 molecules

  3. Given 3.5 moles of sodium chloride, how many grams do you have?

    answer = 200g NaCl

  4. What is the mass of 6.02 x 1023 molecules of silver nitrate?

answer = 170g silver nitrate


     Setting up the factor-label problem is just as important as the answer.

     Form the habit of working neatly, canceling units, and circling the answer.

     Remember, units are just as important as numbers in the answer.