chemical quantities
DESCRIPTION
CHEMICAL QUANTITIES. All Roads Lead to the Mole. Measuring doughnuts: 1 dozen = 12 doughnuts (count) 1 dozen = 500 g doughnuts (mass) 1 dozen = 1 box doughnuts (volume). Measuring steam (H 2 O gas): 1 mole = 6.02 x 10 23 H 2 O molecules (count) 1 mole = 18.0 g H 2 O (mass) - PowerPoint PPT PresentationTRANSCRIPT
Chemical Quantities
• Measuring doughnuts:o 1 dozen = 12 doughnuts (count) o 1 dozen = 500 g doughnuts
(mass)o 1 dozen = 1 box doughnuts
(volume)• Measuring steam (H2O gas):o 1 mole = 6.02 x 1023 H2O molecules
(count)o 1 mole = 18.0 g H2O (mass)o 1 mole = 22.4 L H2O (volume) at
STP
Dozen: Baker as Mole: Chemist
Count Amedeo Avogadro• 1776-1856• Lawyer who became interested in
math and physics• Discovered that equal volumes of
different gases contained an equal number of particles.
• 9 years after his death, Joseph Loschmidt determined a constant and named it after Avogadro.
AVOGADRO’S CONSTANT= 6.02 x 1023
1 mole = 6.02 x 1023 particles1 mole = molar mass (grams)1 mole (of a gas at STP) = 22.4 L
The MOLE is to chemists as the DOZEN is to bakers.
Believe it or not, students all over the country celebrate National Mole Day!
National Mole Day Foundation, INC.
Mole Day
5 Pound Bag of Sugar contains 6.6 moles Of C12H22O11 1 Liter bottle of Water contains 55.5 moles H206.02 x 1023 Grains of Sand: Would be more than all of the sand on Miami Beach.6.02 x 1023 Blood Cells: Would be more than the total number of blood cells found in every human on earth. 6.02 x 1023 Watermelon Seeds: Would be found inside a melon slightly larger than the moon.6.02 x 1023 Pennies: Would make at least 7 stacks that would reach the moon.6.02 x 1023 Donut Holes: Would cover the earth and be 5 miles (8 km) deep.
Types of Representative Particles
• Molecules (breaks down into atoms)• Atoms• Formula Units (breaks down into ions)• Ions
Naming Representative Particles
Pure Substance
Element
Monotomic
Charged
ION
Neutral
ATOM
Polyatomic
MOLECULE
Compound
Molecular
MOLECULE
Ionic
FORMULA UNIT
Naming Representative ParticlesExamples: Name the representative particle for each substance given. For each molecule, state how many atoms are present. For each formula unit, state how many ions make up the ionic compound.
H+:
Cl2:
C2H6:
Cu(NO3)2:
Al:
NaCl:
ION
MOLECULE – 2 ATOMS per molecule
MOLECULE – 8 ATOMS
FORMULA UNIT – 3 IONS per Form.U.
ATOM
FORMULA UNIT – 2 IONS per Form.U.
Mole R.P. Calculations
1 mole = Avogadro’s Number = 6.02 x 1023 R.P.’s
R.P.mol 1
R.P.106.02 23
R.P.106.02mol 1
23
R.P. Example 1:How many moles are in 1.4 x 1022 molecules of H2O?
OH molecules1002.6mol1OH molecules104.1
223
222
OH mol 023.0 2
R.P. Example 2:How many representative particles are in 2.6 mol CO2?
2
223
2
CO mol 1CO molecules 106.02CO mol 6.2
224 CO molecules 106.1
R.P. Example 3:How many atoms are in 5.2 mol CO2?
22
223
2
CO molecule 1atoms3
CO mol 1CO molecules106.02CO mol 2.5
atoms104.9 24
Molar Mass … a.k.a. Molecular Weight (MW)
molar mass = mass of 1 mole of substance
Molar mass can be determined by adding up the atomic masses from the periodic table.
MW Example 3:
Find the MW of MgSO4•7H2O.
=Mg + S + 4O + 7(H2O)=24.3 + 32.1 + 4(16.0) + 7(18.0)=246.4 g/mol
What is the mass of one mole of table salt (NaCl)?
a) 23.0 gb) 35.5 gc) 58.5 gd) 100.0 g
Atomic mass Na = 23.0 g/molAtomic mass Cl = 35.5 g/molMass of one mole of NaCl = 23.0 + 35.5 = 58.5 g
Mole Mass Calculations
1 mole = molar mass (MW) in grams
Massmol 1
(g) massmolar
(g) massmolar mol 1
Mass Example 1:Mass Example 1: How many grams are in 7.20 moles of dinitrogen trioxide?
MW of N2O3 = 2N + 3O = 2(14.0) + 3(16.0) = 76.0 g/mol
1 mole = 76.0 g N2O3
Dinitrogen trioxide = N2O3
3232 ON g547
1.00molg0.76ON mol20.7
Mass Example 2:Mass Example 2: Find the number of moles in 92.2 g of iron(III) oxide, Fe2O3.
MW of Fe2O3 = 2Fe + 3O = 2(55.8) + 3(16.0) = 159.6 g/mol
1 mole = 159.6 g Fe2O3
Iron (III) oxide = Fe2O3
3232 OFe mol578.0
159.6gmol00.1OFe g2.92
What is the mass of 3.7 moles of NaCl?a) 15.8 gb) 58.5 gc) 216.5 gd) 6.02 x 1023 g
gmolgmol 5.216NaCl 5.58
1NaCl 7.3
What is the mass of one mole of water (H2O)?
a) 3.0 gb) 16.0 gc) 17.0 gd) 18.0 g
Atomic mass H = 1.0 g/molAtomic mass O = 16.0 g/molMass of one mole of H2O = 2(1.0) + 16.0 = 18.0 g
How many moles are in 152 g of water?a) 0.118 molb) 8.44 molc) 2736 mold) 6.02 x 1023 mol
molgmolg 44.8
OH 0.181
1OH 152
2
2
Mole Volume Calculations1 mole = 22.4 L of gas at STP
STP = standard temperature and pressure (0 °C & 1 atm)
Volumemol 1
L 22.4
L 22.4mol 1
Volume Example 1:Volume Example 1: Determine the volume, in liters, of 0.600 mol of SO2 gas at STP.
mol 1L4.22(g)SO mol600.0 2
2SO L4.13
Volume Example 2:
Volume Example 2: Determine the number of moles in 33.6 L of He gas at STP.
L 22.4mol 1He(g) 3.6L3
He mol 50.1
Density
Density = Mass / Volume
When given the density of an unknown gas, one can multiply by the molar volume to find the MW. The MW can allow for identification of the gas from a list of possibilities.
Density Example (part A):
The density of an unknown gas at STP is 2.054 g/L. (a) What is the molar mass?
massmolar memolar voludensity
1molL4.22
L2.054g
g/mol 01.46
Density Example (part B):
The density of an unknown gas is 2.054 g/L. (b) Identify the gas as either nitrogen, fluorine, nitrogen dioxide, carbon dioxide, or ammonia.
MW = 46.0 g/mol (from part a)
Nitrogen = N2 = 2(14.0) = 28.0 g/mol
Fluorine = F2 = 2(19.0) = 38.0 g/mol
Nitrogen dioxide = NO2 = 14.0 + 2(16.0) = 46.0 g/mol
Carbon dioxide = CO2 = 12.0 + 2(16.0) = 44.0 g/mol
Ammonia = NH3 = 14.0 + 3(1.0) = 17.0 g/mol
Mixed Mole Conversions
1 mole = 6.02 x 1023 RP’s = MW = 22.4 L of gas @STP
All Roads Lead to the Mole.
Always convert to units of moles first when converting between grams, liters, and representative particles.
Mixed Mole Example 1:
How many carbon atoms are in a 50.0-carat diamond that is pure carbon? Fifty carats is the same as 10.0 g.
C mol 1atoms1002.6
C 12.0gmol 1g0.10 23
C atoms 1002.5 23