Bling Bling: if I were to give each of you one atom of gold for every second that has elapsed since...
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Transcript of Bling Bling: if I were to give each of you one atom of gold for every second that has elapsed since...
Bling Bling: if I were to give each of you one atom of gold for every second that has elapsed since the Dinosaur’s went extinct 65 million years ago,
how much gold would you have?
Moles
• Not to be confused with this very happy individual.
• In Chemistry a mole is defined as 6.022x1023 particles of a substance.
How many eggs are in a dozen?
• How many apples are there in a dozen?
• If a dozen students get detention, how many students have detention?
• Dozen = 12 units
Moles
• 6.022 x 1023 is known as Avogadro’s number.
• Just as a dozen of any substance equals 12 units of that substance, a mole of any substance equals 6.022 x 1023 units of that substance.
Avogadro’s number is a MEASURED number.
• Avogadro: equal volumes of different gases at STP have the same number of particles
• Avogadro’s Number is the number of atoms in 12.01 grams of carbon.
• If we know the charge of one electron and the total charge of one mole of a substance very accurately, we can calculate the number of electrons in a mole of electrons.
MOLAR MASS
1s22s22p63s23p64s23d6
26
FeIRON
55.85
• The atomic mass of iron is 55.85 AMUs.
• This number also represents the molar mass of Iron.
• Iron has a mass of 55.85 grams per mole.
MOLAR MASS
1s22s22p63s23p64s23d6
26
FeIRON
55.85
This is the molar mass of any single element
Unit: g/mol
What is the molar mass of
• Gold• Mercury• Argon• Oxygen• Sulfur• Hydrogen
What is the molar mass of
• Gold• Mercury• Argon• Oxygen• Sulfur• Hydrogen
• 197g/mol• 200.6g/mol• 39.95g/mol• 32g/mol (diatomic)• 32.07g/mol• 2g/m (diatomic)
Concept Check
• How many atoms are there in a mole of gold atoms?
• How many atoms are there in a mole of silver atoms?
79
AuGold
197
47
AgSilver
107.9
Concept Check
• How many atoms are there in a mole of gold atoms?
• How many atoms are there in a mole of silver atoms?
79
AuGold
197
47
AgSilver
107.9
1 mol = 6.022 x1023 units
Give me One Mole of Iron
If I asked you for one mole of iron, how would you do it?
Weigh out 55.85g of iron
• How many atoms of iron would you be giving me?
• A mol is defined as 6.022 x 1023 particles
26
FeIRON
55.85
Give me 3.63 moles of iron?
If I asked you for 3.63 moles of iron, how would you do it?
The same way you would give me 4 dozen of something
units 48dozen 1
units 12dozen 4
By Using Conversion Factors
Converting 3.63 Moles Fe to grams
Fe 202.7gFe mol
Fe 55.85gFe 3.63mol
How many moles is 512 grams of iron?
We solve this again using conversion factors and the molar mass of iron.
Converting 512g Fe to moles.
Fe 9.17molFe 55.85g
Fe 1molFe 512g
How many atoms are in 9.17mol Fe?
Fe atoms10 x 55.2
Fe 1mol
Fe atoms 10 x 6.022Fe 9.17mol
23
23
How many moles are in 25 x 1024 atoms of Fe?
Fe 41.5mol
Fe atoms 10 x 6.022
Fe 1molFe atoms 10 x 25
2324
Mole Worksheets
• 1, 2
Compounds have Molar Mass
H20
H H O
1g/mol 1g/mol 16g/mol
1g/mol + 1g/mol + 16g/mol = 18g/mol
Table Salt
NaCl
Na+ Cl-
23g/mol 35.5g/mol
23g/mol + 35.5g/mol =58.5g/mol
Molar Mass of Sucrose
C12H22O11
C H O
12(12g/mol) 22(1g/mol) 11(16g/mol)
12(12g/mol) + 22(1g/mol) + 11(16g/mol) = 342.3g/mol
Molar Mass of Magnesium Nitrate
Mg(NO3)2
Mg N O
24.3g/mol 2(14.01g/mol) 6(16g/mol)
24.3g/mol + 2(14.01g/mol) + 6(16g/mol) = 148.3g/mol
Mole worksheet
• 3
Molecular Mass
• Molar mass is for the average atomic mass but molecular is for a single molecule but atoms come in different isotopes….
How many moles is 512g of water?
• Convert 512g H20 ---> moles
€
512g H2O∗1mol
18g= 28.4mol H2O
We can Convert Molecules
• Convert 7.5mol H20 ---> grams
OH g351OH 1mol
OH 18gOH 7.5mol 2
2
22
Activity: 1 Cup of Water ~236ml
• How many grams is it?
• What is its molecular mass?
• How many moles is it?
• How many molecules of H2O are there?
• How many total atoms?
• All you need for this is a periodic table and a calculator
Worksheet
• 4
Moles and Volume at STP
STP = Standard Temperature and Pressure
TEMPERATURE: 273.15 K (0 °C, 32 °F)
PRESSURE: 100 kPa (14.504 psi, 0.987 atm, 1 bar).
Remember: volume is proportional to temperature!
Calculating Gas Density
• What is the density of ammonia gas, NH3, at STP?
• First we need the molar mass for ammonia;
14.01 + 3(1.01) = 17.04 g/mol
• The molar volume NH3 at STP is 22.4 L/mol.
• Density is mass/volume:
= 0.761 g/L17.04 g/mol22.4 L/mol
Calculating Gas Density
• What is the density of, O2, at STP?
• First we need the molar mass for O2;
2(16g/mol) = 32 g/mol
• The molar volume O2 at STP is 22.4 L/mol.
• Density is mass/volume:
= 1.4 g/L32 g/mol22.4 L/mol
Calculating Gas Volume• What is the Volume of 5 moles of He at STP?
• First we need the molar mass for He;
He = 4 g/mol
• The molar volume of He at STP is 22.4 L/mol.
He 112LHe 1mol
He 22.4LHe 5mol
Calculating Moles From Volume
• How many moles is 5 Liters of N2 gas at STP?
• The molar volume of N2 at STP is 22.4 L/mol.
22
22 N 0.223mol
N 22.4L
N 1mol N 5L
Molar Mass of a Gas• We can also use molar volume to calculate the
molar mass of an unknown gas.
• 1.96 g of an unknown gas occupies 1.00L at STP. What is the molar mass?
• We want g/mol, we have g/L.
1.96 g1.00 L
22.4 L1 mole× = 43.9 g/mol
Mole Unit Factors
• We now have three interpretations for the mole:
– 1 mol = 6.02 × 1023 particles
– 1 mol = molar mass
– 1 mol = 22.4 L at STP for a gas
• This gives us 3 unit factors to use to convert between moles, particles, mass, and volume.
Mole-Volume Calculation
• A sample of methane, CH4, occupies 4.50 L at STP. How many moles of methane are present?
• We want moles, we have volume.
• Use molar volume of a gas: 1 mol = 22.4 L
4.50 L CH4 × = 0.201 mol CH4
1 mol CH4
22.4 L CH4
Mass-Volume Calculation
• What is the mass of 3.36 L of ozone gas, O3, at STP?
• We want mass O3, we have 3.36 L O3.
• Convert volume to moles then moles to mass:
= 7.20 g O3
3.36 L O3 × ×22.4 L O3
1 mol O3 48.00 g O3
1 mol O3
Molecule-Volume Calculation
• How many molecules of hydrogen gas, H2, occupy 0.500 L at STP?
• We want molecules H2, we have 0.500 L H2.
• Convert volume to moles and then moles to molecules:
0.500 L H2 ×1 mol H2
22.4 L H2
6.02×1023 molecules H2
1 mole H2
×
= 1.34 × 1022 molecules H2
Conclusions
• Avogadro’s number is 6.02 × 1023 and is one mole of any substance.
• The molar mass of a substance is the sum of the atomic masses of each element in the formula.
• At STP, 1 mole of any gas occupies 22.4 L.
Conclusions Continued• We can use the following flow chart for mole
calculations:
Bling Bling: if I were to give each of you one atom of gold for every second that has elapsed since the Dinosaur’s went extinct 65 million years ago,
how much gold would you have?