Uploaded August 2025 | Updated September 2026, 2 weeks ago
Calculating Molar Mass
Dr. DeBacco
Items Needed…
Chemical Formula
Periodic Table
Calculator
Water (H2O) will be the example…
Step 1: Chemical Formula
1. Write down the chemical formula of the compound.
Step 2: Find Atomic Masses
2. Look up the atomic masses of each element in the formula on the periodic table.
Note: usually given in atomic mass units (amu), which are numerically equivalent to g/mol for molar mass.
Step 3: Multiple by Number of Elements
3. Multiply the atomic mass of each element by the number of times it appears in the formula.
Step 4: Sum Total
4. Add up all the contributions to get the total molar mass in grams per mole (g/mol).
Example 2: Carbon Dioxide
Find the molar mass of Sodium Carbonate (Na2CO3)
The chemical formula of Sodium Carbonate is Na2CO3.
It contains…
Two sodium (Na) atoms
One carbon (C) atom
Three oxygen (O) atoms
Molecular weights…
Sodium (Na) is 22.98g/mol
Carbon (C) is 12.011 g/mol
Oxygen (O) is 16 g/mol.
Find the molar mass of Sodium Carbonate (Na2CO3)
Na = 2 × 22.98 = 45.96 g/mol
C = 1 × 12.011 = 12.011 g/mol
O = 3 × 16 = 48 g/mol
Molecular Weight of Na2CO3 =
45.96 + 12.011 + 48 = 105.971 amu
Link to Lecture Slides: drive.google.com/file/d/1xTvyC9vgN7-1L7WERmfBubClsgLM39a8/view?usp=drive_link
*Due to the description character limit the full work cited for "Calculating Molar Mass" can be viewed at... docs.google.com/document/d/1yUPV1xBM7F9sKQ0beNpDSeo6kgey3pVC/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
Calculating Molar Mass
Dr. DeBacco
Items Needed…
Chemical Formula
Periodic Table
Calculator
Water (H2O) will be the example…
Step 1: Chemical Formula
1. Write down the chemical formula of the compound.
Step 2: Find Atomic Masses
2. Look up the atomic masses of each element in the formula on the periodic table.
Note: usually given in atomic mass units (amu), which are numerically equivalent to g/mol for molar mass.
Step 3: Multiple by Number of Elements
3. Multiply the atomic mass of each element by the number of times it appears in the formula.
Step 4: Sum Total
4. Add up all the contributions to get the total molar mass in grams per mole (g/mol).
Example 2: Carbon Dioxide
Find the molar mass of Sodium Carbonate (Na2CO3)
The chemical formula of Sodium Carbonate is Na2CO3.
It contains…
Two sodium (Na) atoms
One carbon (C) atom
Three oxygen (O) atoms
Molecular weights…
Sodium (Na) is 22.98g/mol
Carbon (C) is 12.011 g/mol
Oxygen (O) is 16 g/mol.
Find the molar mass of Sodium Carbonate (Na2CO3)
Na = 2 × 22.98 = 45.96 g/mol
C = 1 × 12.011 = 12.011 g/mol
O = 3 × 16 = 48 g/mol
Molecular Weight of Na2CO3 =
45.96 + 12.011 + 48 = 105.971 amu
Link to Lecture Slides: drive.google.com/file/d/1xTvyC9vgN7-1L7WERmfBubClsgLM39a8/view?usp=drive_link
*Due to the description character limit the full work cited for "Calculating Molar Mass" can be viewed at... docs.google.com/document/d/1yUPV1xBM7F9sKQ0beNpDSeo6kgey3pVC/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
