1. Moles and Molar Mass
Objective: I will be able to convert moles of a substance to mass and mass to moles.
Entry Task:
The LD50 for arsenic (III) oxide, As2O3, is 15 mg/kg.
Figure out the lethal dose for a 150 lb adult (1 kg = 2.2 lb)
How many molecules do you think are in a lethal dose? What would you need to know to figure this out?

2. Mass of an atom, mass of a mole of atoms
Atomic mass of 1 atom (from periodic table):
Mass of C = amu
Mass of As = amu
Mass of O = 16 amu
Actual mass of 1 mole:
Mass of 1 mol C atoms = g
Mass of 1 mol As atoms = g
Mass of 1 mol O atoms = 16 g

3. Mass of molecules Atomic Mass of Molecules (add mass of all atoms):
Mass of CO2 = = amu
Mass of As2O3 = = amu
1 mol of CO2 = 1 mole of C atoms and 2 moles of O atoms
1 mol of As2O3 = 2 moles of As atoms and 3 moles of O atoms
Actual mass of 1 mole:
Mass of 1 mol CO2 = = g
Mass of 1 mol As2O3 = = g

4. What is the mass of 1 molecule of...
PbCl2 =
H2O =
C12H22O11 =
CaCO3 =
= amu
= amu
12(12.011) + 22(1.01) + 11(16) = amu
= amu

5. What is the mass of 1 MOLE of...
PbCl2 =
H2O =
C12H22O11 =
CaCO3 =
= g
= g
12(12.011) + 22(1.01) + 11(16) = g
= g
Mass of 1 mole of a substance is known as the MOLAR MASS

6. What are the Molar Masses of:
Name of drug
Chemical formula
Molar Mass
Adult dose
Moles in adult dose?
acetomen-iphen
C8H9NO2
500 mg
aspirin
C9H8O4
325 mg
ibuprofen
C13H18O2
400 mg
151.2 g
mol
180.2 g
mol
206.3 g
mol

7. Moles-Mass conversions
Mass to moles:
# of moles (mol) = mass(g) / molar mass(g/mol)
Moles to mass:
mass(g) = # of moles(mol) x molar mass(g/mol)
I have an 11g sample of Cl2. How many moles do I have?
I have 3.0 moles of MgO. What mass does the sample have?
11g / (g/mol) = 0.16 mol
3 mol x (g/mol) = g

8. Exit Ticket
Methadone is a medication used as a painkiller and as a treatment for those recovering from heroin addiction. The LD50 for methadone is 95 mg/kg.
Would you consider methadone to be more or less toxic than acetomenaphen (LD50 = 2404 mg/kg)? Than aspirin (LD50 = 200 mg/kg)?
Explain how you would calculate the amount of methadone that would be lethal to a human.