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chloe ko.
christina chow.
mr. doktor's chemistry class
block g

home. mrdoktor.

Density

• Density is a measure of mass per volume

               d = m
                      v

• measured in g/L or g/mL

examples:

• an unknown compund has a molar mass of 22.0g/mol. If 0.15 mol occupies a volume of 25mL determine the compound's density.

    d = m                0.15mol x 22.0g = 3.3 g
           v                                1 mol
               
                             3.3g = 0.13 g/mL
                            25mL

• The density of Sodium is 2.80g/mL. An solid piece of sodium has a volume of 48.0mL. Determine the number of atoms present.

                 2.80g  x 48.0 mL = 134.4 g
                   mL

                134.4g x 1 mol =  5.8mol
                               23.0g
           
               5.8 mol x 6.02 x 10^23 = 3.52 x 10^24
                                   1 mol

Density of gases

• The density of gases varies with temperature
• At STP we can find density by:

                MM (molar mass)  
             22.4 L (molar volume)

example

• calculate the density of C₂ at STP

            24.0g/mol   = 1.07g/L
            22.4L/mol

http://www.youtube.com/watch?v=9OOkctlj5n0

heres a handy video to show how to solve a mole mass equation! :)

~ Chloe >_<