- Mass - Mole - Numbers
Avogadro's number, the mole concept, formul weights and molar
mass allow us to convert among masses, moles and number of atoms
or molecules. For example suppose we have 25 g of acetic acid
(C2H4O2). The molar mass of acetic acid is 60 g/mol. we can ask
the following questions for 25 g of acetic acid:
We can answer these questions in the following way:
many moles of acetic acid?
||= 25 g x (1 mol acetic acid/60 g) = 0.417 mol
many moles of carbon?
2x0.417 mol = 0.834 mol of C
|How many moles of hydrogen?
||= 4x0.417 mol = 1.67
mol of H
|How many moles of oxygen?
||= 2x0.417 mol = 0.834
mol of O
|How many total moles of atoms?
||= 8x0.417 mol = 3.34
mol of atoms
|How many carbon atoms?
||= 0.834 mol x(6.022x10^+23/mol) = 5.02x10^+23 C atoms
|How many hydrogen atoms?
||= 1.67 mol x(6.022x10^+23/mol) = 1.01x10^+24 C atoms
|How many oxygen atoms ?
||= 0.834 mol x(6.022x10^+23/mol) = 5.02x10^+23 O atoms
|How many total atoms?
||= 3.34 mol x(6.022x10^+23/mol) = 2.01x10^+24 total atoms
Alternatively, we could have started with a number of molecules,
and then convert this number to number of C atoms, mass of C
atoms, moles of C atoms, total moles etc.. The procedure for
this calculation is similar to that above..