Chapter 10_ Chemical Quantities Mole – Volume Relationships by malj

VIEWS: 18 PAGES: 8

									   Chapter 10:
Chemical Quantities

  Mole – Volume
  Relationships
    Mrs. Russotto
   Mole – Volume Relationships
 • Because gases easily change volume
   depending on conditions, we need to define
   where we are taking our measurements
    – Called STP (standard temperature and pressure)
    – Temperature - 0°C
    – Pressure – 101.3 kPa (kilopascals) or 1 atm
      (atmosphere)

• At STP 1 mol of a gas occupies 22.4 L.
   – Known as molar volume
   – Used to convert a known number of moles of gas to the
     volume of the gas at STP.


• 22.4 L = 1 mol at STP is the conversion factor
   Calculating the Volume of a
            Gas at STP
• Determine the volume, in liters, of
  0.60 mol SO2 gas at STP.

   Known                         Unknown
   0.60 mol SO2                  ? L SO2
   1 mol SO2 = 22.4 L SO2

   0.60 mol SO2    22.4 L SO2              =
                   1 mol SO2

           13.44 L SO2      = 13 L SO2
    Try this with your partner…
• What is the volume of 3.70 mol N2 at STP?
• Answer: 82.9 L N2
    Calculating moles of a Gas
       from volume at STP
• At STP, how many moles does 28.0 L of helium
  contain?
   Known                       Unknown
   28.0 L He                   ? mol He
   1 mol He = 22.4 L He



   28.0 L He       1 mol He               =
                   22.4 L He

           1.25 mol He
    Try this with your partner…
• How many moles of carbon dioxide are present in
  7.50 liters?
• Answer: 0.335 mol CO2
 Calculating Molar Mass from Density
• Can calculate molar mass of gas using
  density and molar volume
• Molar mass = density X molar volume
• Example: The density of a gaseous compound
  containing carbon and oxygen is found to be 1.964
  g/L at STP. What is the molar mass of the compound?


   Known                           Unknown
   Density = 1.964 g/L             Molar mass = ? g/mol
   1 mol (gas at STP) = 22.4 L


 1.964 g          22.4 L
                                 = 44.0 g/mol
  1L              1 mol
        Try this with your partner…
• A gaseous compound of sulfur and oxygen has a
  density of 3.58 g/L at STP. What is the molar mass of
  this gas?
• Answer: 80.2 g/mol

								
To top