the mole. matter can be measured in 3 ways: counting particles mass volume
DESCRIPTION
SI unit, measures the amount of substance 602,213,670,000,000,000,000,000 A mole of pennies would be $6,022,136,700,000,000,000,000 six sextillion, twenty-two quintillion, one hundred thirty-six quadrillion, seven hundred trillion dollars 6.02 x 10 23TRANSCRIPT
CHAPTER 10The Mole
10.1 MEASURING MATTER Matter can be measured in 3 ways:
Counting particles Mass Volume
MOLE SI unit, measures the amount of substance 602,213,670,000,000,000,000,000
A mole of pennies would be $6,022,136,700,000,000,000,000
six sextillion, twenty-two quintillion, one hundred thirty-six quadrillion, seven hundred trillion dollars
6.02 x 1023
AVOGADRO’S NUMBER 6.02 x 1023
The number of representative particles in one mole of a pure substance
REPRESENTATIVE PARTICLES Atoms
Right off periodic table 7 elements exist only as diatomic
molecules (H2 N2 O2 F2 Cl2 Br2 I2)
Molecules Covalently bonded
Formula Units Ionic Compounds
ONE MOLE OF Fe = 6.02 x 1023 atoms
H2O = 6.02 x 1023 molecules
CaCl2 = 6.02 x 1023 formula units
MOLES REPRESENTATIVE PARTICLES
Conversion factor = 6.02 x 1023 particles
1 mole
How many atoms are in 2.00 mol of argon?
How many molecules are in 7.25 mol of carbon dioxide?
How many formula units are in 3.15 mol of sodium oxide?
REPRESENTATIVE PARTICLES MOLES
How many moles are in 1.62 x 1023 atoms of argon?
How many moles are in 4.35 x 1024 molecules of dinitrogen triflouride?
MOLAR MASS Mass of one mole of a substance
g/mol Mass of atoms is found on the periodic
table K =
Mass of compounds must be calculated H20 CO2
CALCULATING MOLAR MASS What is the molar mass of barium
acetate?
What is the molar mass of ammonium sulfate?
MASS MOLES How many moles are in 12.5 g of
Carbon dioxide?
How many moles are in 83.2 g of H2SO4?
MOLES MASS What is the mass in grams of 1.5 mol of
sodium chloride?
What is the mass in grams of 0.774 mol of oxygen?
MOLAR VOLUME STP
Standard temperature and pressure T = 0 oC P = 1 atmosphere (atm)
At STP 1 mole of gas occupies a volume of 22.4L
22.4L = molar volume of a gas
22.4L of a gas contains 6.02 x 1023 particles of that gas.
MOLES VOLUME What is the volume of 1.50 mol of
nitrogen at STP?
What is the volume of 3.75 mol of helium at STP
VOLUME MOLES How many moles are in 75.3 L of water
vapor at STP?
How many moles are in 250 L of nitrogen dioxide at STP?
CONVERTING BETWEEN UNITS Must ALWAYS go to moles first
Moles
Particles
Volume
Mass
Particles
Volume
Mass
How many atoms are in a 44.3 g piece of iron?
What is the volume of 5.24 x 1022 molecules of iodine?
What is the volume of 68.4 g of fluorine gas at STP?
How many molecules are in 0.75 L of nitrogen gas at STP?
What is the mass in grams of 2.301 L of sodium phosphate?
What is the volume of 17.3 g of NH3 gas at STP?
PERCENT COMPOSITION The percent by
mass of each element in a compound
The percents of all the elements should add up to 100
CALCULATING PERCENT COMPOSITION1. Find the total molar mass of each
element in the compound.2. Find the molar mass of the entire
compound.3. Divide the total molar mass of each
element by the molar mass of the compound then multiply by 100
4. Check that all your percentages add up to 100
EXAMPLE: C3F6
1. Total mass of C = total mass of F =
2. Mass of compound C3F6 =
3. % of C = % of F =
4. Check your work!
What is the percent composition of H2SO4?
10.2 EMPIRICAL AND MOLECULAR FORMULAS
Empirical formula – shows the smallest whole-number ration of atoms in a compound
Molecular formula – gives the actual number of each kind of atom in a molecule
C6H12O6
CALCULATING EMPIRICAL FORMULA1. Change % to g (assume 100 g of
compound so 30% = 30 g)2. Convert each element from g to moles3. Divide each mole amount by the
smallest number from step 24. Change to a whole number = subscript
in empirical formula
EXAMPLE: 30.5% N AND 69.5% O1. g of N = g of O =
2. Convert to moles
3. Divide
4. Formula =
EXAMPLE: 43.7 % P AND 56.3 % O
8.7 MOLECULAR FORMULAS To find the molecular formula you must
know Empirical formula Molar mass of compound
Can be the same as the empirical formula but often is not
CALCULATING MOLECULAR FORMULA1. Calculate the mass of the empirical
formula
2. Divide molar mass of compound by mass of empirical formula
3. Multiply each subscript in the empirical formula by the answer from step 2
EMPIRICAL = NO2, MOLAR MASS = 92 G/MOL
1. Mass of NO2 =
2.
3. Molecular formula =
An unknown compound contains 58.5% carbon, 9.8% hydrogen, and 31.4% oxygen. Its molar mass is 102 g/mol. What are its empirical and molecular formulas?