Question: How many moles are in 1000 g of sucrose?
1. Obtain the atomic mass
First, write down the formula for sucrose: C12H22O11
2. Calculate the molar mass of sucrose
To calculate the molar mass of a substance, you must use the periodic table. Look for the atomic mass of each element present in the compound. Then use a table such as the one below to calculate the the sum of the atomic masses of the compound’s constituent atoms.
|Element||Symbol||Atomic mass (amu)||#n atoms||Mass|
|Hydrogen||H||1.008||22||22(1.008) = 22.176 amu|
|Carbon||C||12.01||12||12(12.01) = 144.12 amu|
|Oxygen||O||16.00||11||11(16.00) = 176.00 amu|
|Molecular mass of sucrose
= (22.176 + 144.12 + 176.00)
= 342.296 amu
The molar mass of sucrose is simply the molecular mass expressed as g/mol.
Molar mass of sucrose = 342.296 g/mol
3. Calculate the number of moles
Apply the formula to calculate the number of moles
The answer can be rounded to 3 mol.
(Note: The symbol for mole is “mol”)
Usefulness of moles
- Knowing the number of moles allows you to calculate the number of atoms if you are dealing with chemical compounds.
- Moles are very useful, they allow chemists to use chemical equations to determine the mass of reactants and products.
Read about Avogadro Constant