Chemistry NotesTwo Step Problems

In Review

The mole is an SI unit of measure

for amount of particles.

6.02x1023 particles = 1 mole

molar mass = 1 mole

22.4L (@STP) = 1 mole

Two Step Problems

We have now discussed moles in

three ways: as particles

(1 mol = 6.02x1023 particles),

as a mass ( molar mass = 1 mol)

and as a volume (22.4 L = 1 mol)

Two Step Problems

To get from particles to grams,

grams to liters or particles to

liters of a substance, two steps

are required, with moles always

in between!

Try one on your own…

How many particles of H2O are

there in 0.25 g?

Try one on your own…

How many particles of H2O are

there in 0.25 g?

0.25 g H2O x 1 mole H2O x 6.02 x 1023 particles H2O = 8.4 x 1021 particles H2O

18.0148 g H2O 1 mole H2O

Try one on your own…

How many liters of CO2 are in 12.3 g?

Try one on your own…

How many liters of CO2 are in 12.3 g?

12.3 g CO2 x 1 mole CO2 x 22.4 L CO2 = 6.26 L CO2

44.009 g CO2 1 moleCO2

Try one on your own…

How many grams of Fe2O3 are in

5.5x1024 formula units?

Try one on your own…

How many grams of Fe2O3 are in

5.5x1024 formula units?

5.5x1024 formula units x 1 mole Fe2O3 x 159.691 g Fe2O3 = 1,500 g Fe2O3

6.02 x 1023 form. units 1 mole Fe2O3