December 12-Density and Moles/Density of Gas

Density and Moles

These are the equations for density.
-density is measured in g/L or g/mL


EX.
How many moles are in 11.5mL of water? (H2O=18)

11.5g x 1mol = 0.639g<---don't forget about
             18 g                       significant digits




EX.
A small sample of silver contains 1.23x10(23) silver atoms. If the density is 10.5g/mL what is the volume of the silver sample?
-this is a multi-step conversion so you will have to go from atoms->moles->mass->density

1.23x10(23) atoms x      1mol      x 107.9g x 1mL = 2.1mL
                                 6.02x10(23)    1mol      10.5g

Density of Gas

-@STP we can find density by:
   mm                molar mass-->g/mol
22.4L/mol        molar volume-->L/mol

EX.
Determine the density of methane(CH4=16g) at STP.

16g
1mol  = 0.71g
22.4L
mol

Janine Roldan