Chapter 8: Chemical Composition
Difference Between Atomic Mass and Molar Mass
-molar mass is the mass of one mole per single element while atomic mass is the mass of an atom at rest or is the number of protons and neutrons.
-molar mass is measured in grams per mole while atomic mass is “unitless.”
website:
http://www.differencebetween.net/science/difference-between-molar-mass-and-atomic-mass/
This websites provides a better understanding on the differences between atomic mass and molar mass.
Calculating Molar Mass of Compounds
calculation:
Find the molar mass of Fe2O3
Fe - 2 x 55.85 = 111.70
O - 3 x 16.0 = 48.0
111.70+48.0 = 159.6 g/mol
website:
http://www.occc.edu/kmbailey/chem1115tutorials/Stoichiometry_Molar_Mass.htm
This website provides a helpful lesson on learning how to calculate molar mass.
activity:
http://www.chemteam.info/Mole/MolarMass.html
This activity gives more practice on calculating molar mass. (scroll to bottom of page for problems and answers)
video:
http://www.youtube.com/watch?v=yqqZ4XYG1vI
This video goes into a deeper understanding of calculating molar mass with helpful examples.
The Concept of a Mole; Conversion Between Grams and Moles, Moles and Atoms
-mole: the unit all chemists use in describing number of atoms
-Avogadro's number - one mole of something consists of 6.022X10^23 units of that substance
calculations:
1. determine the number of moles of CO2 in 454 grams
-The atomic mass of C is 12.01 and the atomic mass of O is 16.00
The formula mass of CO2 is:
120.01 + 2(16.00) = 44.01
moles CO2 = 454g x 1 mole/44.1g = 10.3 moles
10.3 moles CO2
2. determine the number of atoms of Fe in 1x10^-9 g
-The atomic number mass of Fe is 55.85g
1.0x10^-9gFe x (1mol Fe/55.85g Fe) (6.022x10^23 atoms/1 mol Fe) =
6.022x10^14/55.85 = 1.08x10^13 atoms
website:
http://chemistry.about.com/od/dictionariesglossaries/g/defmole.htm
This website goes into a further understanding of learning how to convert moles to grams and moles to atoms.
activity:
http://www.sciencegeek.net/Chemistry/taters/Unit4GramMoleVolume.htm
This activity gives more practice in learning how to convert moles to grams and moles to atoms.
video:
http://www.youtube.com/watch?v=NMdN1LtHuDA
This video gives a better understanding of how to learn to convert with moles.
Percent Composition of Compounds (Mass Percent)
-mass percent is one way of representing to concentration of an element in a compound or a component in a mixture
-mass percent is calculated as the mass of a component divided by the total mass of the mixture, multiplied by 100
calculation:
Calculate the mass percent composition of each element in Potassium Ferricynaide (K3Fe(CN)6)
-step 1: find the atomic mass of each element in the molecule
-Atomic mass of K: 39.10 g/mol
-Atomic mass of Fe: 55.85 g/mol
-Atomic mass of C: 12.01 g/mol
-Atomic mass of N: 14.01 g/mol
-step 2: find the mass combination of each element
-mass of K = 3(39.10) = 117.30 g/mol
-Mass of Fe = 55.85 g/mol
- Mass of C = 6(12.01) = 72.06 g/mol
- Mass of N = 6(14.01) = 84.06 g/mol
-step 3: find the total molecular mass of the molecule (molecular mass is the sum of the masses of each element)
- 117.30+55.85+72.06+84.06=329.27g/mol
-step 4: find the mass percent composition of each element
-mass percent of K = 117.30/329.27X100 = 35.62%
-mass percent of Fe = 55.85/329.27x100 = 16.96%
- mass percent of C = 72.06/329.27x100 = 21.88%
-mass percent of N = 84.06/329.27x100 = 25.53%
answer: K3Fe(CN)6 is 35.62% potassium, 16.96% iron, 21.88% carbon and 25.53% nitrogen
activity:
http://www.softschools.com/quizzes/chemistry/stoichiometry_percent_composition/quiz1128.html
this activity helps practice problems with solving mass percent. It gives a better way to understand the concept.
video:
http://www.youtube.com/watch?v=zhquOhw3c98
This video provides a deeper understanding of solving mass percent composition.
Empirical Formulas
-the formula of a compound that expresses the smallest whole-number ratio of the atoms present is the empirical formula
calculation:
-you are given a compound such as methyl acetate
-contains 48.64% carbon (c), 8.16% hydrogen (H), and 43.20% oxygen (O)
-step 1: change each percentage to an expression of the mass of each element in grams
-C becomes 48.64 g C
-H becomes 8.16g H
-O becomes 43.20 g O
-step 2: covert the amount of each element in grams to its amount in moles
- (48.64/1)(1/12.01) = 4.049 mol
- (8.16/1)(1/1.008) = 8.095 mol
- (43.20/1)(1/16.00) = 2.7 mol
-step 3: divide each of the found values by the smallest of these values (2.7 mol)
- (4.049/2.7) = 1.5
- (8.095/2.7) = 3
- (2.7/2.7) = 1
-step 4: if necessary, multiply these numbers by integers in order to get whole numbers; if an operation is done to one of the numbers, it must become to all of them
- 1.5x2=3
-3.2=6
-1x2=2
-the empirical formula of methyl acetate is C3H6O2
activity:
http://gtz.unitedisd.org/www/frco_fchs/site/hosting/academics/science/chem/Practice%20Problems/stoichiometrypractice/empirical%20practice.htm
This activity provides practice problems that will give a better understanding on finding of empirical formula of a compound.
video:
http://www.youtube.com/watch?v=eHR9saDmeYk
This video gives a deeper understanding on how to find the empirical formula of a compound.
Difference between Empiricla Formula and Molecular Formula
-the formula of a compound that expresses the smallest whole number ratio of the atoms present is called the empirical formula
- the actual formula of a compound is called the molecular formula
Difference Between Atomic Mass and Molar Mass
-molar mass is the mass of one mole per single element while atomic mass is the mass of an atom at rest or is the number of protons and neutrons.
-molar mass is measured in grams per mole while atomic mass is “unitless.”
website:
http://www.differencebetween.net/science/difference-between-molar-mass-and-atomic-mass/
This websites provides a better understanding on the differences between atomic mass and molar mass.
Calculating Molar Mass of Compounds
calculation:
Find the molar mass of Fe2O3
Fe - 2 x 55.85 = 111.70
O - 3 x 16.0 = 48.0
111.70+48.0 = 159.6 g/mol
website:
http://www.occc.edu/kmbailey/chem1115tutorials/Stoichiometry_Molar_Mass.htm
This website provides a helpful lesson on learning how to calculate molar mass.
activity:
http://www.chemteam.info/Mole/MolarMass.html
This activity gives more practice on calculating molar mass. (scroll to bottom of page for problems and answers)
video:
http://www.youtube.com/watch?v=yqqZ4XYG1vI
This video goes into a deeper understanding of calculating molar mass with helpful examples.
The Concept of a Mole; Conversion Between Grams and Moles, Moles and Atoms
-mole: the unit all chemists use in describing number of atoms
-Avogadro's number - one mole of something consists of 6.022X10^23 units of that substance
calculations:
1. determine the number of moles of CO2 in 454 grams
-The atomic mass of C is 12.01 and the atomic mass of O is 16.00
The formula mass of CO2 is:
120.01 + 2(16.00) = 44.01
moles CO2 = 454g x 1 mole/44.1g = 10.3 moles
10.3 moles CO2
2. determine the number of atoms of Fe in 1x10^-9 g
-The atomic number mass of Fe is 55.85g
1.0x10^-9gFe x (1mol Fe/55.85g Fe) (6.022x10^23 atoms/1 mol Fe) =
6.022x10^14/55.85 = 1.08x10^13 atoms
website:
http://chemistry.about.com/od/dictionariesglossaries/g/defmole.htm
This website goes into a further understanding of learning how to convert moles to grams and moles to atoms.
activity:
http://www.sciencegeek.net/Chemistry/taters/Unit4GramMoleVolume.htm
This activity gives more practice in learning how to convert moles to grams and moles to atoms.
video:
http://www.youtube.com/watch?v=NMdN1LtHuDA
This video gives a better understanding of how to learn to convert with moles.
Percent Composition of Compounds (Mass Percent)
-mass percent is one way of representing to concentration of an element in a compound or a component in a mixture
-mass percent is calculated as the mass of a component divided by the total mass of the mixture, multiplied by 100
calculation:
Calculate the mass percent composition of each element in Potassium Ferricynaide (K3Fe(CN)6)
-step 1: find the atomic mass of each element in the molecule
-Atomic mass of K: 39.10 g/mol
-Atomic mass of Fe: 55.85 g/mol
-Atomic mass of C: 12.01 g/mol
-Atomic mass of N: 14.01 g/mol
-step 2: find the mass combination of each element
-mass of K = 3(39.10) = 117.30 g/mol
-Mass of Fe = 55.85 g/mol
- Mass of C = 6(12.01) = 72.06 g/mol
- Mass of N = 6(14.01) = 84.06 g/mol
-step 3: find the total molecular mass of the molecule (molecular mass is the sum of the masses of each element)
- 117.30+55.85+72.06+84.06=329.27g/mol
-step 4: find the mass percent composition of each element
-mass percent of K = 117.30/329.27X100 = 35.62%
-mass percent of Fe = 55.85/329.27x100 = 16.96%
- mass percent of C = 72.06/329.27x100 = 21.88%
-mass percent of N = 84.06/329.27x100 = 25.53%
answer: K3Fe(CN)6 is 35.62% potassium, 16.96% iron, 21.88% carbon and 25.53% nitrogen
activity:
http://www.softschools.com/quizzes/chemistry/stoichiometry_percent_composition/quiz1128.html
this activity helps practice problems with solving mass percent. It gives a better way to understand the concept.
video:
http://www.youtube.com/watch?v=zhquOhw3c98
This video provides a deeper understanding of solving mass percent composition.
Empirical Formulas
-the formula of a compound that expresses the smallest whole-number ratio of the atoms present is the empirical formula
calculation:
-you are given a compound such as methyl acetate
-contains 48.64% carbon (c), 8.16% hydrogen (H), and 43.20% oxygen (O)
-step 1: change each percentage to an expression of the mass of each element in grams
-C becomes 48.64 g C
-H becomes 8.16g H
-O becomes 43.20 g O
-step 2: covert the amount of each element in grams to its amount in moles
- (48.64/1)(1/12.01) = 4.049 mol
- (8.16/1)(1/1.008) = 8.095 mol
- (43.20/1)(1/16.00) = 2.7 mol
-step 3: divide each of the found values by the smallest of these values (2.7 mol)
- (4.049/2.7) = 1.5
- (8.095/2.7) = 3
- (2.7/2.7) = 1
-step 4: if necessary, multiply these numbers by integers in order to get whole numbers; if an operation is done to one of the numbers, it must become to all of them
- 1.5x2=3
-3.2=6
-1x2=2
-the empirical formula of methyl acetate is C3H6O2
activity:
http://gtz.unitedisd.org/www/frco_fchs/site/hosting/academics/science/chem/Practice%20Problems/stoichiometrypractice/empirical%20practice.htm
This activity provides practice problems that will give a better understanding on finding of empirical formula of a compound.
video:
http://www.youtube.com/watch?v=eHR9saDmeYk
This video gives a deeper understanding on how to find the empirical formula of a compound.
Difference between Empiricla Formula and Molecular Formula
-the formula of a compound that expresses the smallest whole number ratio of the atoms present is called the empirical formula
- the actual formula of a compound is called the molecular formula