# Chapter 10_ Chemical Quantities Mole – Volume Relationships by malj

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```									   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
• What is the volume of 3.70 mol N2 at STP?
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
• How many moles of carbon dioxide are present in
7.50 liters?
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