How to solve chemical compound problems in Algebra
What are chemical compounds?
In this lesson you’ll learn how to find the molar mass of chemical compounds given the molar mass of individual atoms, and how to find the molar mass of individual atoms given the molar mass of a compound or molecule.
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Remember, the molecular mass of a compound or molecule is the mass of a group of individual atoms that come together to make the compound or molecule. You can find the molar mass by adding the molar mass of each individual atom in the molecule or compound. (Don’t forget that there could be more than one of each type of atom.)
Molar mass is measured in grams per mole which can be abbreviated g/mol, or in atomic mass units which can be abbreviated amu, or just u.
Solving chemical compound problems in Algebra using ratios and proportions
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Finding molar mass for one molecule of a chemical compound
Example
Find the molar mass for one molecule of table sugar in grams per mole.
Table sugar has the molecular formula ???\text{C}_{12}\text{H}_{22}\text{O}_{11}???
Carbon has a mass of ???12.01??? g/mol
Hydrogen has a mass of ???1.01??? g/mol
Oxygen has a mass of ???16.00??? g/mol
You can see that one molecule of table sugar ???\text{C}_{12}\text{H}_{22}\text{O}_{11}??? has ???12??? Carbon, ???22??? Hydrogen and ???11??? Oxygen atoms.
Multiply each number of atoms by their corresponding molar mass and add them up.
Carbon ???12(12.01) = 144.12??? g/mol
Hydrogen ???22(1.01) = 22.22??? g/mol
Oxygen ???11(16.00) = 176.00??? g/mol
Find the total.
???144.12 + 22.22 + 176.00 = 342.34??? g/mol
Let’s look at an example where we know the total molar mass but we want the molar mass of an individual atom.
You can find the molar mass by adding the molar mass of each individual atom in the molecule or compound.
Example
What is the molar mass of Cadmium in one mole of Cadmium Carbonate?
Cadmium Carbonate is written as ???\text{CdCO}_3??? and it’s made of Cadmium, Carbon and Oxygen
???\text{CdCO}_3??? has a molar mass of about ???172.42??? g/mol
Carbon has a mass of ???12.01??? g/mol
Oxygen has a mass of ???16.00??? g/mol
Cadmium Carbonate has ???172.42??? grams in one mole. The chemical formula is made of ???1??? Cadmium atom with an unknown molar mass, ???1??? Carbon atom with a molar mass of about ???12.01??? g/mol and ???3??? Oxygen atoms each with a molar mass of about ???16.00??? g/mol.
Let’s set up what we know and what we don’t know.
Cadmium: ???1(\text{molar mass of Cadmium})=1x??? g/mol
Carbon: ???1(12.01) = 12.01??? g/mol
Oxygen: ???3(16.00) = 48.00??? g/mol
???\text{CdCO}_3???: ???172.42??? g/mol
Now let’s set up an equation to solve for the molar mass of Cadmium in Cadmium Carbonate.
???x + 12.01 + 48.00 = 172.42???
???x+60.01=172.42???
???x = 112.41??? g/mol
In this case we know the molar mass of cadmium is ???112.41??? g/mol because there was only one Cadmium atom in Cadmium Carbonate.
