6.4 Molar Mass
Molar Mass of Elements
 The molar mass of an element is equal to the mass given of the periodic table
 The units for molar mass (M) is g/mol
 Determine the molar mass for the following elements:
o Ne = 1 x 20.18g/mol = 20.18g/mol
o O2 =
o P4 =
o S8 =
Molar Masses of Compounds
 We can calculate the molar mass of a compound by adding together me molecular mass of each atom
in the compound.
 Determine the molecular mass for the following compounds:
o H3PO4 = 3(1.01)+ 30.97 + 4(16.00) = 98.00g/mol
o NaCl =
o Na2SO4 =
o CaCl22H2O =
Deriving the formula to determine moles:
 Molar mass units = g/mol.
 What other measurement can we use to determine the number of moles?
 So if we know mass in g and molar mass in g/mol what is our formula for determining moles?
 n=m/M
Converting amount to mass
 m=nM
Examples:
 According to the manufacturer, a typical can of cola contains 40.0 g of sucrose, C12H22O11 Calculate
the amount of sucrose in 40.0 g.
o What do know?
o What to we need to know?
o What is our formula?
 Find M
 Use n=m/M
 A litre of human blood typically contains 4.0 mmol of glucose, C6H12O6. Calculate the mass of this
amount of glucose.
o What is our formula?
o What do we know?
o What do we need to know?
 Find M=
 m=nM =
Homework:
Mole follow-up Worksheet
p.257 practice 1, p.277 practice 1abc, 2abc, p. 277 #1, 4abc, 5-11