7.2 more mole conversions!!!. - molecular oxygen = o 2 - atomic oxygen = o from the periodic table 7...
TRANSCRIPT
7.2
More Mole Conversions!!!
- Molecular Oxygen = O2
- Atomic Oxygen = O from the periodic table
7 elements that exist as diatomic molecules (MEMORIZE)
Molar Mass
• The mass in grams of 1 mol of a substance.
• Molar Mass is found using the periodic table!!!
What is the molar mass of nitrogen gas? (N2)
2 (14g) = 28 g
1 mol of a substance = molar mass of a substance
Example: What is the molar mass of nitrogen gas, N2?
1 mol N2
28 g N2
Another Example• What is the molar mass of molecular oxygen,
O2?
2 (16g) = 32 g
Knowing molar mass is important because it allows us to make the
following conversions:
mass mol representative particle
Ex. 1 Example problem
• How many grams are in 2 mol of nitrogen gas?
• Given: 2 mol N2
• Known: 1 mol N2= 28g N2
Mol mass2 mol N2 28 g N2 = 56 g N2
1 mol N2
EX.2 How many molecules are in 84 g of nitrogen gas?
• Given: 84 g N2
• Known: 1 mol N2 = 28 g N2
1 mol N2 = 6.02 x 1023 molecules N2
Mass mol molecules
How many molecules are in 84 g of nitrogen gas?
• Given: 84 g N2
• Known: 1 mol N2 = 28 g N2
1 mol N2 = 6.02 x 1023 molecules N2
Mass mol molecules84 g N2 1 mol N2 6.02 x 1023 molecules N2
28 g N2 1 mol N2
= 1.806 x 1024 molecules
Your Turn Ex.3: Find the number of moles in 176 g of CO2.
• Given:• Known:
Road Map:
Your Turn Ex.3: Find the number of moles in 176 g of CO2.
• Given: 176 g CO2
• Known: 44 g CO2 = 1 mol CO2
Road Map: Mass Mol
Your Turn Ex.3: Find the number of moles in 176 g of CO2.
• Given: 176 g CO2
• Known: 44 g CO2 = 1 mol CO2
Road Map: Mass Mol
176 g CO2 1 mol CO2 = 4 mol CO2
44 g CO2
Ex. 4 Find the mass of 1.2 x 1024 molecules of NaCl
Given: 1.2 x 1024 molecules NaClKnown:
Road Map:
Ex. 4 Find the mass of 1.2 x 1024 molecules of NaCl
Given: 1.2 x 1024 molecules NaClKnown: 1 mol = 6.02x1023 molecules NaCl1 mol NaCl = 58 g NaClRoad Map:
Molecules mol mass
Ex. 4 Find the mass of 1.2 x 1024 molecules of NaCl
Given: 1.2 x 1024 molecules NaClKnown: 1 mol = 6.02x1023 molecules NaCl1 mol NaCl = 58 g NaClRoad Map:
Molecules mol mass1.2 x 1024 molecules NaCl 1 mol NaCl 58 g NaCl
6.02x1023 molecules 1 mol NaCl NaCl
Volume of a mol of a gas at STP
STP: (standard temperature and pressure)0°C or 273 K1 atm or 101.3 kPa
1 mol of a gas occupies 22.4 L
1 mol or 22.4 L22.4L 1 mol
Ex. 5 Determine the volume in L of 2 mol of oxygen gas at STP.
• Given: 2 mol O2
• Known: 1 mol O2 = 22.4 L
Work:
Ex. 5 Determine the volume in L of 2 mol of oxygen gas at STP.
• Given: 2 mol O2
• Known: 1 mol O2 = 22.4 L
Work:2 mol O2 22.4 L = 44.8 L O2
1 mol O2
Your turn! Ex. 6 Determine the number of moles in 67.2 L of oxygen
gas. • Given: 67.2 L O2
• Known:
Your turn! Ex. 6 Determine the number of moles in 67.2 L of oxygen
gas. • Given: 67.2 L O2
• Known: 1 mol O2 = 22.4 L
Work 67.2 L O2 1 mol O2 = 3 mol O2
22.4 L
Now we have a big road map….
Volume (L)
# representativeMass moles particles
Ex. What is the volume of 8 g of O2?
Given: 8 g of O2
Known:
Ex. What is the volume of 8 g of O2?
Given: 8 g of O2
Known: 1 mol O2 = 32 g O2
1 mol O2 = 22.4 L
Road Map: Mass Mol volume
8 g of O2 1 mol O2 22.4 L = 5.6 L
32 g O2 1 mol O2
How much volume does 1.8 x 1024 molecules of Cl2 at STP occupy?
Road Map Molecules mol volume
How much volume does 1.8 x 1024 molecules of Cl2 at STP occupy?
Road Map Molecules mol volume
1.8 x 1024 molecules of Cl2 1 mol Cl2 22.4 L
6.02 x 1023 Cl2 1 mol Cl2
= 67.2 L
Density = mass/volume
Units: grams / L
• When given density, you can calculate molar mass using the volume of 1 mol.
g 22.4 L gL 1 mol mol
The End!!!