Chapter 10: Chemical Quantities

The Mole

What is a mole?The SI unit that represents the amount

of a substance that contains 6.02 x 1023 representative particles of that substance.

What is Avogadro’s Number? The number of particles contained in

one mole of a substance.6.02 x 1023 particles602,000,000,000,000,000,000,000

What is a Representative Particle? Atom:

The smallest particle of an element Molecule:

Group of atoms joined together by covalent bonds

Formula unit:Lowest ratio of elements in ionic bonds

Particle:This word can be used for any of the above

words

Atomic or Formula Mass Mass of one single representative particle

of a substance Measured in atomic mass units (amu)

How do you find Atomic or Formula Mass? Add up the amu for every part of the

substance: Find the amu on the Periodic Table

C

12.01 amu

NaCl

22.99 amu + 35.45 amu = 58.44 amu

H2O

(1.01 amu x 2) + 16.00 amu =

18.02 amu

Molar Mass The mass of one mole of any substance

Measured in grams/ mole Same as finding atomic mass, but change amu to

grams.

C 12.01 amu = 12.01 g/molNaCl58.44 amu = 58.44 g/mol

H2O18.02 amu = 18.02 g/mol

Converting # of Particles to # of Moles

Formula:

# of moles =

# of particles x

1 mole6.02 x 1023 particles

Sample Problem:

How many moles of NaCl are in 3.01x1023 formula units of NaCl?

Converting # of Moles to # of Particles

Formula:

# of particles =

# of moles x 6.02 x 1023 particles 1 mole

Sample Problem:

How many particles are in 3 moles of water?

Converting # of Moles to Mass

Formula:

Mass (g) =

# of moles x Molar mass (g) 1 mole

Sample Problem:

What is the mass of 1 mole of LiOH?

Converting Mass to # of Moles

Formula:

# of moles =

Mass (g) x 1 mole Mass (g)

Sample Problem:

How many moles of NaCl are in 174.22 grams of NaCl?

Mole-Volume Relationship

Avogadro’s Hypothesis:At standard temperature and pressure (STP)

1 mole of any gas occupies the same volume.STP: 0oC and 1 atm

At STP, 1 mole or 6.02 x 1023 particles, of ANY gas, has a volume of 22.4 L.

22.4 L is called the molar volume of a gas.

Converting # of Moles of gas to Volume

Formula:

Volume of gas =

moles of gas x22.4 L 1 mole

Sample Problem:

What is the volume, in liters, of 0.60 mol of SO2 gas at STP?

Converting Volume of gas to Moles

Formula:

Moles of gas =volume of gas x

1 mole 22.4 L

Sample Problem:

If you collect 8.00 L of O2 gas, how many moles have you collected?

Calculating Molar Mass from Density

Formula:

=22.4 L 1 mole

grams mole

grams L

Molar mass

Density

Sample Problem:

What is molar mass of a gas with a density of 2.86 g/L at STP?

Percent Composition of a Substance Percent Composition=

Mass of element in the compound x 100

Molar Mass of Compound

Sample Problem

 Find the % composition of H and O in water