The Molar MassLesson 2

Molar Mass

The atomic mass of an element is the relative mass of the element. It is measured in grams and found on the periodic table.

The molar mass is the mass of one mole of particles and the unit is grams/mole.

Let’s see where to find it on the periodic table!

Formula Molar Mass (g/mol)

1H 1.0 g/mole

4.0 g/moleHe

CO2 more than one atom ???

To find the Molar Mass

Consider the molar mass of all the atoms involved:

CO2

1 ( 12.0 ) + 2 (16.0)

= 44.0 g/mole.

Formula Molar Mass (g/mol)

1H 1.0 g/mole

4.0 g/moleHe

CO244.0 g/mole

Fe2O3

To find the molar mass:

Fe2O3

2 (55.8) + 3 (16.0)

= 159.6 g/moles.

TRY: Find the molar mass of:

Ni2(CO3)3

Formula Molar Mass (g/mol)

1H 1.0 g/mole

4.0 g/moleHe

CO244.0 g/mole

Fe2O3159.6 g/mole

Al(NO3)3 .5H2O

Ni2(CO3)3297.4 g/mole

Al(NO3)3 .5H2O

1 ( 27.0) + 3 (14.0) + 9 (16.0) + 10 (1.0) + 5 (16.0)

Al N O H O

303.0 g/mole

TRY: Find the molar mass of

Lead(II) iodate

Conversion factors are back!

Particles Moles Grams

1.00 mole = 6.02 x 1023 particles Molar Mass

From Periodic Table? g / mole

The molar mass is a new conversion factor that can convert between grams and molesAvogadro’s number is another conversion factor that can convert between moles and particles

Convert 56.6 grams of C to moles.

Don’t forget sig figs!

3 sig figs

= 4.72 molesx 1 mole12.0 g

56.6 g

Convert 6.9 moles of PbO2 into grams

= 1.7 x 103 g

1 molex 239.2 g6.9 moles

Two-StepMole Calculations

Convert 2.00 g CH4 into molecules

grams moles molecules

= 7.51 x 1022 moleculesx 6.02 x 1023 molecules1 mole16.04 g

x 1 mole2.00 g CH4

Convert 9.56 x 1026 molecules Cl2 into grams.

molecules moles grams

= 1.13 x 105 g x 71.0 g

6.02 x 1023 molec

x 1 mole 9.56x1026 molec Cl2

1 mole

Try: Convert 692.5 grams Na2CO3 into molecules.

g moles molecules

Try: Convert 8.66 x 1024 particles of CaCl2 into grams

particles moles g

Happy Mole day to You

Homeworkpage 80 page 84

#6 a, c, e , g , i , k, p #15 b, c, g

#7 a, c

Page 82#8 b, f, I

#9 a, h, g