Calculating Molar Mass
• On the periodic table, the atmoic mass given is the
mass (in grams) of one mole of that atom.
– Sodium (Na) Molar Mass = 22.99 g
– Magnesium (Mg) = ____ g
What about molecules?
• NaCl
• has one of each atom
• = 23 + 35.5 = 58.5 g in one mole of NaCl
• H20
• has 2 hydrogen and 1 oxygen
• = 2 (1) + 16 = 18 g in one mole of H20
• You need to be very careful when counting
the number of atoms of each element in a
molecule.
• Count the number of atoms for each element
in the molecule:
• Ca(OH)2
• Na2(CO3)
• CH3OH
Find the molar mass
•
•
•
•
•
NH3
CO3
HCl
Mg(OH)2
Fe3(PO4)2
Converting moles to mass
• Determine the molar mass of one mole of
that molecule
• Use a conversion factor
• 1 mole = ____ g (of that molecule or atom)
Determine the number of moles:
• 25 g Li
• 251 g F2
• 345 g 5(H20)
Determine the mass:
• 1.25 moles of Na
• 2.63 moles of CuSO4
• 0.73 moles of Mg(OH)2
Volume
• 1 mole = 22.4 L
• How many grams are there in 28.6 L of carbon
monoxide?