Density and Moles

Density
-Density is a measure of mass per volume d = m
                                                                      V
-measured in g/L or g/mL

Example
-Water has a density of 1.0g/mL. Determine the mass of 11.5mL of water
-How many moles are in 11.5mL of water?

1.0g/mL x 11.5mL = 11.5g
11.5g x 1 mol = 0.64 mol
             18 g

Density of Gases

-The density of gases varies with temperature

-At STP we can find density by:  MM              molar mass               

                                               22.4L/mol        molar volume

Example
-Calculate the density of 02 STP

32.0g/mol = 1.43g/L
22.4L/mol

-An unknown diatomic gas has a density of 1.696g/mol STP
 -Find its molar mass
 -What is the chemical formula

1.696g/L x 22.4L/ 1 mol = 37.99g/mol = 38g/mol
                                                                  2
                                                            = 19g/mol
Chemical formula : F2