Mole Conversions: Molecules to Atoms

Objectives You will be able to…  Distinguish molecules and atoms  Convert from moles of a compound to # atoms total  Convert from of a compound to # atoms of a specific element. Massachusetts Chemistry Content Standard 5.3

Mole Conversion Map  U use use Avogadro’s Molar Number Mass (counting) (measuring) MoleUnitsGrams

Molecules vs. Atoms  Molecules and atoms can both be considered “units” in terms of the Mole Map.  So how can we tell which is which?  Well, what is the definition of a molecule? A molecule is 2+ atoms chemically combined.  So, a molecule is larger than an atom.  A molecule may consist of 2+ different atoms OR  It may consist of 2+ atoms of the same element.

Molecules vs. Atoms  If the substance is composed of 2+ elements, then it is a compound and the units are called molecules. Such as CO 2 and H 2 O and C 6 H 12 O 6  If the substance is made of only one element, BUT that element has a subscript following it, the units are also called molecules. Such as H 2 and N 2 and Cl 2

How many atoms are in a molecule of…?  CO 2 3  NH 3 4  C 6 H 12 O 6 24 O3O3 3

Let’s try a conversion… 1) What is the total number of atoms in 0.78 mol of H 2 O? (Hint: determine the # of molecules of H 2 O first!)

Let’s try a conversion… 1) What is the total number of atoms in 0.78 mol of H 2 O? 0.78 mol x x10 23 mc x 1 mol

Let’s try a conversion… 1) What is the total number of atoms in 0.78 mol of H 2 O? 0.78 mol x x10 23 mc x 3 atoms = 1 mol 1 mc

Let’s try a conversion… 1) What is the total number of atoms in 0.78 mol of H 2 O? 0.78 mol x x10 23 mc x 3 atoms = 1 mol 1 mc 1.4 x atoms

Let’s try a conversion… 2) How many carbon atoms are in 1.25 mol of glucose? What’s the formula for glucose? C 6 H 12 O 6

Let’s try a conversion… 2) How many carbon atoms are in 1.25 mol of glucose?C 6 H 12 O mol x x mc x 1 mol

Let’s try a conversion… 2) How many carbon atoms are in 1.25 mol of glucose?C 6 H 12 O mol x x mc x 6 C atoms = 1 mol 1 mc

Let’s try a conversion… 2) How many carbon atoms are in 1.25 mol of glucose?C 6 H 12 O mol x x mc x 6 C atoms = 1 mol 1 mc 4.52 x atoms C

Let’s try a conversion… 3) How many hydrogen atoms are in 1.25 mol of glucose? 9.03 x atoms H

Let’s try a conversion… 4) How many oxygen atoms are in 1.25 mol of glucose? 4.52 x atoms O (the same # atoms as carbon atoms!)

So, what’s the trick?  The trick is to identify the type of substance involved—could it be classified as a molecule?  Does the formula have more than one capital letter? If not, its units are just “atoms”. But if so, its units could be called “molecules”— which can then be subdivided into atoms.

Mole Map, Expanded