Editor: Ariweco

Simply put, the mole represents a number. Just as the term dozen refers to the number twelve, the mole represents the number 6.02 x 1023.
Now that's a big number! While a dozen eggs will make a nice omelet, a mole of eggs will fill all of the oceans on earth more than 30 million times over. Think about it: It would take 10 billion chickens laying 10 eggs per day more than 10 billion years to lay a mole of eggs. about numbers of atoms and molecules. Atoms and molecules are very tiny things. A drop of water the size of the period at the end of this sentence would contain 10 trillion water molecules. Instead of talking about trillions and quadrillions of molecules (and more), it's much simpler to use the mole.

Group 1- p. 287-295

Co-editor: Antonio Arimany

Group: Niggachu John, filipino Valley, Anne O'Toole, David O'Brien, Lauren Bedard, Mark Cuddy, Shannon Degnan

Measuring Matter p. 287-288 by Abby John

Problems p.289 by Hannah Valley

Finding Mass from a Count:

What is the mass of 90 average-sized apples if 1 dozen apples has a mass of 2.0kg?

Step 1: List the knowns and unknowns.
  • number of apples = 90
  • 12 apples = 1 dozen
  • 1 dozen apples = 2.0kg
  • mass of 90 apples = ?kg

You can use dimensional analysis to convert the number of apples to the mass of apples.
Carry out this conversion by performing the following sequence of conversions:
Number of apples --> dozens of apples --> mass of apples

Step 2: Solve for the unknown.

The first conversion factor is (1 dozen apples) / (12 apples).
The second conversion factor is (2.0kg apples) / (1 dozen apples).

Mass of apples = 90 apples X 12 dozen apples X 2.0kg apples
12 apples 1 dozen apples
Mass of apples = 15kg apples

The mass of 90 average-sized apples is 15kg.

Practice Examples:
  1. What is the mass of 132 oranges if a half-dozen oranges has a mass of 3.0kg?
  2. What is the mass of a rollercoaster train if it is made up of 6 separate cars, 4 people are allowed on each car,
and each person weighs 25kg?
3. What is the mass of 50 potatoes, in grams, if 8 potatoes have a mass of 1.6kg?

What is a Mole p.290 by Anne O'Toole

  • Chemists use a unit that is a specified number of particles, which is called a mole.
  • A mole (mol) of a substance is 6.02 x 10^23 representative particles of that substance and is the SI unit for measuring the amount of a substance.
  • This is Avogadro's number.
  • Amedeo Avogadro di Quaregna was an Italian scientist who helped clarify the differences between atoms and molecules
  • representative particle refers to the species present in a substance: atoms, molecules, or formula units
  • In most elements, it is the atom.
  • Seven elements (H, N, O, F, Cl, Br, I) diatomic molecules
  • A mole of any substance contains Avogadro's number of representative particles (6.02 x 10^23) representative particles.
  • http://www.fordhamprep.org/gcurran/sho/sho/convert/molecalc.htm

external image moletopart6.jpg
Photo by Anne O'Toole
http://molarmath.info/Images/moletopart6.jpg (photo citation)

Converting Number of Atoms to Moles p.291(Math) David O'Brien

# of atoms = 1.25 X 1023 atoms Mg
1 Mol of Mg = 6.02 X 1023 atoms Mg
Conversion Factor is: 1 Mol Mg / 6.02 X 1023 atoms Mg
You multiply the # of atoms of Mg by the conversion factor to get:
(1.25 X 1023 atoms Mg) X (1 Mol Mg / 6.02 X 1023 atoms Mg) = 0.208 Mol Mg

# of atoms = 2.80 X 1024
1 Mol of Si = 6.02 X 1023 atoms Si
Conversion Factor is: 1 Mol Si / 6.02 X 1023 atoms Si
You multiply the # of atoms of Mg by the conversion factor to get:
(2.80 X 1024 atoms Si) X (1 Mol Si / 6.02 X 1023 atoms Si) = 4.65 Mol Si


Converting Moles to Number of Particles p.291 by Lauren Bedard

  • To determine number of atoms in a compound, must know how many atoms are in a
representative particle of the compound (chemical formula)
  • To find number of atoms in a mole of a compund, first determine number of
representative particles.
6.02 X 1023 representative particles
  • Representative particles= moles X 1 mole
external image mol11.gif

Mass of a Mole of an Element p.293 by Mark Cuddy
~AMU's measure atomic mass
~Atomic masses are based mass of the most common isotope of carbon
~An average atom (with an atomic mass of 12 amu) is 12 times heavier than an average hydrogen atom (that's 1 amu)
~The mass ratio of 12 carbon atoms to 1 hydrogen atom remains the same no matter what unit is used to express the masses
EXAMPLE: 12 grams of carbon atoms and 1 gram of hydrogen atoms must contain the same number of atoms
-Atomic masses are weighted average masses of the isotopes of each element

The atomic mass of an element expressed in grams is the mass of a mole of the element**
The mass of a mole of an element is its MOLAR MASS
EXAMPLE: Carbon's molar mass is 12.0 g
-The molar masses of any two elements must contain the same number of atoms
REMEMBER: the molar mass of any element contains 1 mol, or 6.02 x 10^23 atoms of that element

The MOLE: the amount of substance that contains as many representative particles as the number of atoms
EXAMPLE: 12.0g is the molar mass of carbon-12, therefore 12.0g is 1 mol of carbon
-Molar mass is the the mass of 1 mol of atoms of any element.

(Mark Cuddy)

Mass of a Mole of a Compound p.295 by Shannon Degnan

-To find the mass of a mole, you need to know the formula of the compund
-You need to count the amount of molecules for each letter.
-ex: SO3= s-1, o-3
-You need to find the atomic mass of each element and then multiply it by however many molecules that letter has
-Then add all of the elements in the compound to get the molar mass and add grams
-"to calculate the molar mass of a compound, find the number of grams of each element in one mole of the compund. then add the masses of the elements in the compound"

(Shannon Degnan)

moleformula.gif(Shannon Degnan)

Group 2 p.303-311

Co-Editor: Alex Fischbach

Group: Kelsey Sullivan, Meghan Faber, Lindsey Bedrosian, Grayce Rose, Erin Garrity

p. 302 by Kelsey Sullivan

Calculating Molar Mass from Density

  • Molar Mas = denisty at STP X Molar volume at STP
    • First, List the knowns and unknowns of the problem
    • Next, solve for the unknown
    • Finally, check to make sure your results make sense
  • Calculating Volume at STP
    • volume of gas= moles of gas X the conversion factor

Video: http://www.youtube.com/watch?v=ZqS38Il8--s

P.305 by Alexandra Fischbach

The Mole Road Map

  • Te mole is at the center of your chemical calculations.
  • To convert from one unit to another, you must use the moles as an intermediate step.
  • The form of the conversion factor depends on what you know and what you calculate

The Percent Composition of a Compound

  • The relative amounts of the elements in a compound are expressed

  • Consists of a percent value for each different element in a compound
  • The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound X 100
  • %mass of element = mass of element/mass of compound X 100%

Video: http://www.youtube.com/watch?v=xbEeyT8nK84&feature=related

P.307 by Meghan Faber

Percent Composition from the Chemical Formula

  • You can figure out the percent composition if you know the compound's chemical formula
  • The subscripts can be used to calculate the mass of each element in a mole of the compound
    • The sum of each mass is the molar mass
  • To find the percent by mass of each element in one mole of the compound, divide the mass of each element by the molar mass and multiply by 100%
  • Formula:
%mass = mass of element in 1 mol compound X 100%
molar mass of compound
How to video: http://www.youtube.com/watch?v=xbEeyT8nK84

p.308 by Grayce Rose
Percent Composition as a Conversion Factor
  • you can use percent composition to calculate the number of grams in any given mass of an element in a specific compound.
  • you can do this by multiplying the mass of the compound by a conversion factor based on the peercent composition of the element you are trying to calculate the mass of.
  • use the ratio of:
    • the % of the element that is in the compound / the amount of the compound that the % was calculated from
  • if you add together the masses of all of the invividual elements that you calculated, it should equal the mass of the origional compound
video: http://www.youtube.com/watch?v=AnUG4m1Hv7s

p.309 by Lindsey Bedrosian
I.Imperical Formulas
A. Gives the lowest whole number ratio atoms of the elements in a compound
B. May or may not be the same as the molecular formula.

external image Chapter%207-2.GIF

Picture by Lindsey Bedrosian

P.311 by Erin Garrity

Molecular Formulas
· each element has a different molar mass
· all compounds have different molar mass
>> the molecular formula of a compound is either the same as its determined empirical formula or it is a whole number multiple of the formula (balancing)
· once the empirical formula is determined the molecular mass is needed to determine the molecular formula
· from the empirical formula you can determine the empirical formula mass(emf)

Group 3 p. 297 - 303

Co-Editor: Colleen Fitzgerald

Group: Marybeth Nametz, Erika Paiva, Colleen Fitzgerald, Emily Taylor, Lauren Altmeyer, Kim Kougut, Brendan Lynch

The Mole/Mass Relationship p.297 by Marybeth Nametz

The Molar mass of any substance is the mass in grams of one mole of that substance.
-> this applies to all substances-- elements, molecular compounds, and ionic compounds
-> sometiems the term molar mass is unclear
  • Ex. if you assume, in a problem, that oxygen is molecular oxygen (O2) then the molar mass is 32.0 g (2 X 16.0 g) HOWEVER if yuou assume that, in the problem, that you are looking for the mass of a mole of oxygen atoms (O), then the answer would be 16.0. Completely different.
->this confusion can be avoided by using the formula of the substance.

Use the molar mass of an element or compound to convert between the mass of a substance and the moles of a substance.
  • the conversion factor for the calculation is based on the relationship that the Molar mass=1 mol
  • To calculate the masss in grams of a given number of moles:

mass (grams) = number of moles x mass (grams)
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1 mole

You can calculate the number of moles using the same relationship of 1 mol= 1 molar mass
  • This time the conversion factor is inverted
moles = mass (grams) x 1 mole

external image gram-molecular-mass.gif(By Marybeth Nametz http://www.tutorvista.com/content/chemistry/chemistry-ii/stoichiometry/gram-molecular-mass.php)

Mole to Mass p.298 by: Erika Paiva

Converting Moles to Mass

- To calculate the moles of a substance to mass, use this formula :
mass (grams) = number of moles X mass(grams)/ 1 mole

1. Analyze - list the known and the unknown information

2. Calculate- solve for the unknown

3. Evaluate- does the result make sense?

Example Problem:

What is the mass of 9.45 mol of aluminum oxide?

1. Analyze

known: number of moles= 9.45 mol Al2O3
unknown: mass= ? g Al2O3

2. Calculate

Determine the molar mass of Al2O3: 1 mol Al2O3= 102.0 g Al2O3

mass= 9.45 mol Al2)3 X 102.0g Al2O3/ 1 mol Al2O3= 964g Al2O3

3. Evaluate

The answer should be about 1,000 g and has been rounded to the correct number of significant figures.

Moles to Mass worksheet

Picture and link By: Erika Paiva
external image 16826138.png

Mass to Moles p.299 by: Colleen Fitzgerald

  • Moles = mass(grams)x 1 mole/mass(grams)
  • Example: How many moles of Iron III oxcide are contained in 92.2 g of pure Fe?
  • 3 steps- Analyze the known and unknown then solve for the unknown then make sure the result makes sense
  • Analyze- List the known and unknown
  • You know the mass (92.2gFe2O3) but not how many moles you need
  • Calculate- Next you need to calculate and solve for the unknown
  • moles=92.2gFe2O3x 1molFe2O3/ 159.6 gFe2O3= 0.578 mol Fe2O3
  • Evaluate- after completing the problem make sure the numbers make sense
  • Extra practice problems:
  • 1. Find the number of moles in 3.70x10-1
  • 2. Calculate the number of moles in 75.0 g of dihydrogen nitrogen.
  • Mass to Moles

external image AAAUAUN0.JPG

Colleen Fitzgerald :http://wps.prenhall.com/wps/media/objects/165/169519/GIFS/AAAUAUN0.JPG
Video:Mass to Moles

The Mole/Volume Relationship p. 300 by: Emily Taylor
  • In 1811, Amedeo Avogadro (Avogadro's Hypthesis) stated that equal volumes of gases at the same temperature and pressure have the same number of particles, but those particles are not the same size because they make up different gases.
  • The particles in all gases are so far apart that if the particles are relatively large, they don't need much more space than smaller particles.
  • The volume of gas varies based on the temperature change and the pressure change.
  • Standard temperature and pressure (STP) means a temperature of 0(degrees) C and a pressure of 101.3 kPa, or 1 atmosphere (atm.)
  • At STP, 1 mol or 6.02 X 10 ^23 representative particles, of any gas occupies a volume of 22.4 L.
  • The quantity, 22.4 L is called the molar volume of a gas.

The image below shows gas particles reacting to a different temperature.
external image gas_pressure.gif

Clip by Emily Taylor. Link:http://www.ucolick.org/~bolte/AY4_00/week6/sun_fusion.html

Calculating the Volume of a Gas at STP p. 301 by: Lauren Altmeyer

Sulfur dioxide (SO2) is a gas produced by burning coal. It is an air pollutant and one of the causes of acid rain

Determine the volume, in liters, of 0.60 mol SO2 gas at STP.

1. Analyze- List the knowns and the unknown.
Knowns Unknowns
  • Moles= 0.60 mol SO2 * volume= ? L SO2
  • 1 mol SO2= 22.4 L SO2
Use the relationship 1 mol SO2 = 22.4 L SO2 (at STP) to write the conversion factor needed to convert moles to volume
Conversion Factor= 22.4 L SO2 / 1 mol SO2

2. Calculate- Solve for the unknown.
Volume = 0.60 mol SO2 x 22.4 L SO2 / 1 mol SO2 = 13 L SO2
  • cross out the labels

3. Evaluate- Does the result make sense?
Because 1 mol of any gas at STP has a volume of 22.4 L, 0.60 mol should have a volume sightly larger than one half of a mole or 11.2 L. The answer should have two sig figs.

By: Lauren Altmeyer

Calculating Molar Mass of a Gas at STP p. 302 by: Kim Kogut

The density of a gaseous compound containing carbon and oxygen is found to be 1.964 g/L at STP (standard temperature and pressure).

What is

the molar mass of the compound?

1. Analyze - List the knowns and unknowns
Density = 1.964 g/L
1 mol (gas at STP) = 22.4 L (This will be our conversion factor.)
Molar mass = ?g/mol

2. Calculate - Solve for the unknown
molar mass = 1.964 g/1 L x 22.4 L/1 mol
=44.0 g/mol

3. Evaluate - Does the answer make sense?
The ratio of 44.0 g to 22.4 L is about two, which is close to the known density. The answer should also have three significant figures.

The Mole Road Map p.303 by: Brendan Lynch
external image application.pdf(picture by brendan lynch)
The mole is at the center of your chemical calculations. to convert from one unit to another you must use the mole as an intermediate step. The form of the conversion factor depends on what you know and what you want to calculate.
Just decide what you are starting with and what you want to figure out. Then find those two points on the map above and follow the roads.
The roads represent the steps you will have to do and the conversion factors you will need to know in order to accomplish what you want.

^^ a video explaining the mole road map. (clip by brendan lynch)