Oct. 21st /2009 [THE Christian Bondoc]

Herro.

Atomic Mass

• The mass of 1 mole of atoms in an element
• The mass of 1.0 mol of 'C' atoms is 12.0g
• The mass of 1.0mol of 'Ca' atoms 40.1g.

Molecular Mass

• The mass of 1.0 mole of molecules of an element or compound

N2, O2, H2, Br2, Cl2, F2, I2, P4, S8

• Assume the all the rest are monoatomic

(I apologize for the size, when i made it large, part of it got cut off)

Finding the molar mass of compounds

H2O

2 H = 2(1.0) = 2.0

1 O = 1(16.0) = 16.0

18.0g/mol

Find the molar of ammonium phosphate

NH4+

PO4 3-

(NH4)3PO4

3 N = 3(14.0) = 42

12H = 12(1.0) = 12

1P = 1(31.0) = 31

4O = 4(16.0) = 64

149g/mol

Converting mass <----> Moles

Conversion factor g/mol or mol/g

Find the mass of 2.5mols of water

H20 -> 18.0g/mol

(1mol/18.0g) x (1/2.5mol)

(1 mol/18.0g) x (1/2.5mol)

= 1/45g

= 45g

Find the number of moles in a 391g samples of nitrogen dioxide

NO2

1N = 14(1.0) = 14

2O = 2(16.0) = 32

45g/mol

(391g / mol ) (1 / g) =

(391g / mol) (1/ g) =

(391/mol) (1/46) = 8.5mol

1) Find the mass of 2.5 moles of water.

2H: (2)(1)

1O: (1)(16)

= 18g/mol

2.5 mol • 18.0g /mol= 45g

2) Find the number of moles in a 391g sample of nitrogen dioxide.

1N: (1)(14)

3O: (3)(16)

=45g/mol

391g • 1mol/45g = 8.5 mol

3) 3.6kg of sulphur trioxide = ? mol

11S: (1)(32.1)

3O: (3)(16.0)

= 80.1 g/mol

3.6kg • 1000kg/1g = 3600 g

3600g • 1mol/80.1g = 45mol