Michael V. answered • 03/21/22
College Graduate in Chemistry
Hello,
Molar Mass is the weight (usually in grams) of a single mole of something. For Elements (Molecules that are only one type of atom) it is atomic weight converted to grams.
For Example: The atomic mass of Carbon is about 12 atomic mass units (Depending on the problem you might need less or more precision. It depends on the situation). It is a one-to-one ratio to go from amu (Atomic Mass Units) to grams per mole (Molar Mass). That means that 1 mole of Carbon weighs 12 grams.
For Compounds (Molecules that have different types of atoms) you are just adding up the different atomic weights from the Chemical Formula and converting it to Molar Mass.
An Example of a simple Compound: H2O (Water)
1)There are 2 Hydrogen Atoms and 1 Oxygen Atom
2)A Hydrogen Atom weighs about 1 amu and you have 2.
An Oxygen Atom weighs about 16 amu and you have 1
3)Total Mass of 1 Molecule of Water = (1 x 2) + (16 x 1) = 18 amu
4)Total Mass of 1 Mole of Water = 18 grams
We can write this as 18 grams/mole or 18 g/mol
Your questions are a bit more complicated than this but you will have to do the same steps
1) Determine the different types of Atoms in the molecule
2) Determine the individual atomic weights of each type of atom (Use a Periodic Table)
3) Add the atomic weights of each and every atom together (Make sure you count them all)
4) Convert Atomic Mass to Molar Mass (Remember, it's a 1:1 Ratio)
Follow this pattern and you should be able to solve any of these problems.
Good Luck
