AMU, Molecular and Formula Masses

AMU,Formula/Molecular Masses

By Julia Lequin

The atomic mass is​ the mass of an atom of an element.

The atomic mass of an element is shown in the periodic table.​

​

​

Formula/Molecular Mass

• ​atomic mass is mass of an atom of an element

• How​ about the mass of a compound?

Why is measuring mass is important in Chemistry?​

What is a formula mass? How is it similar and different from molecular mass?​

the sum of the atomic masses of the constituents ​atoms in an ionic compound

​

​

​Formula Mass

(Ionic Compounds)

​

​

​1 Na = 22.99 amu

1 Cl = 35.45​ amu

mass NaCl = 58.44 amu​

​Find the formula mass of sodium chloride?

NaCl​

​

​-round off the massess into two decimal places.

• ​What are the elements in the compound above?

• How many atoms of aluminum?

• How many atoms of nitrogen?

• How many atoms of oxygen?​

​Find the formula mass of aluminum nitrate?

​

Multiple Select

Which are elements are in aluminum nitrate? Check all that apply.

• aluminum

• nitrate

• nitrogen

• oxygen

Multiple Choice

How many atoms of aluminum in an ionic compound, aluminum nitrate?

• 1

• 3

• 6

• 9

Multiple Choice

How many oxygen atoms in the compound aluminum nitrate?

• 1

• 3

• 6

• 9

Multiple Choice

What is the formula mass of aluminum nitrate?

• 56.99 amu

• 117.01 amu

• 184.99 amu

• 213.01 amu

ex. methane gas, CH₄

1 atom carbon = 12.01 amu

4 atoms hydrogen = ​ 4.04 amu

molecular mass of CH₄ = 16.05 amu

​​

​

​

Molecular Mass​

-sum of the atomic masses of​ the atoms in a molecule

​

Remember:

Formula mass for ions

molecular mass for molecules​

​ions are in ionic compounds

molecules are covalent compounds​

​

​some examples of ionic compounds:

​NH₄NO₃

CaCl​₂

some examples of covalent​

glucose molecule (C₆H₁₂O₆)​

water molecule (H₂O)​

​

The finding of formula mass of a compound and molecules are the​ same.

​

-both are about the sum of all the atomic masses of all elements present in a compound(ionic or covalent).

-compound's weight​

Multiple Choice

What is the molecular mass of glucose, C₆H₁₂O₆?

• 29.02 amu

• 174.12 amu

• 180.18 amu

• 200.18 amu

​Moles

-a​n amount of a substance equal to a quantity of 6.02 x 10²³

​

-Avogadro's number (6.02 x 10²³)​

​

​Molar mass is atomic mass or the formula or molecular mass of a substance express in grams.

Find the formula/molecular mass of each substance? Write your answer in your notes?​

​

What did you notice with mole each substance compared to the formula, molecular, and the molar mass of each?​

​