Relating the Moles &
Volume of a Gas
• Hand in labs and pick up your worksheets
Avogadro’s Hypothesis
• Equal volumes of different gases at the same
temperature and pressure contain the same
number of particles
Standard Temperature and
Pressure (STP)
• Pressure = 101.3 kPa = 1 atm (pressure at sea level)
• Temperature = 25°C
• At STP: 1 mol of any gas has a volume of 22.4 L
• Conversion factor: 22.4 L/mol
• Only for gases and only at STP!
• So this is not the same volume as the one in density
unless you are told that it’s a gas and that it is at
STP
Practice
• Hebden p.83 #11 a, b and #12 a, b
Think, Pair, Share
• Try the following problems on your own first
• If you have trouble then talk to your partner
• If both of you still do not feel confident, form a
group of 4 with another pair
Think, Pair, Share
1) How many chloride ions are in 8.3 g of copper(II)
chloride?
2) Calculate the number of hydrogen atoms in 4.5
mol of glycerol, C3H5(OH)3.
3) How many molecules are in 14.56 g of sodium
hydrogen sulfate?
4) Natural gas consists primarily of methane, CH4.
What is the mass of 8.0 L of CH4 at STP?
5) What volume of CO2 at STP contains 0.20 g of
carbon?
Think, Pair, Share
1) How many chloride ions are in 8.3 g of copper(II)
chloride?
CuCl2 molar mass: 63.546+2x35.453 = 134.449 g/mol
8.3g x 1mol/134.449g x 6.022x1023 molec/1mol =
3.717588 x 1022 molec CuCl2
There are 2 Cl atoms for in every 1 molecule of CuCl2
3.717588 x 1022 molec CuCl2 x (2 atom Cl)/(1 molec
CuCl2) = 7.4 x 1022 atoms
Think, Pair, Share
2) Calculate the number of hydrogen atoms in 4.5
mol of glycerol, C3H5(OH)3.
C3H8O
4.5 mol x 6.022x1023 molecules/mol = 2.7099 x 1024
There are 8 atoms of H for every 1 molecule of C3H8O
2.7099 x 1024 x 8 = 2.2 x 1025 atoms
Think, Pair, Share
3) How many atoms are in 14.56 g of sodium
hydrogen sulfate?
NaHSO4
14.56g x 1mol/120.0589g x 6.022x1023 = 7.303x1022
atoms
Think, Pair, Share
4) Natural gas consists primarily of methane, CH4.
What is the mass of 8.0 L of CH4 at STP?
8.0 L x 1mol/22.4L x 16.0426g/mol = 5.7 g
Think, Pair, Share
5) What volume of CO2 at STP contains 0.20 g of
carbon?
0.20g x 1mol/12.011g x 22.4L/mol = 0.37 L