The Mole: The Mole: A Measurement of MatterA Measurement of Matter

Prentice-Hall Chapter 10.1Prentice-Hall Chapter 10.1

Dr. YagerDr. Yager

ObjectivesObjectives DescribeDescribe methods of measuring the amount methods of measuring the amount

of somethingof something

DefineDefine Avogadro’s number as it relates to a Avogadro’s number as it relates to a mole of a substancemole of a substance

DistinguishDistinguish between the atomic mass of an between the atomic mass of an element and its molar masselement and its molar mass

DescribeDescribe how mass of a mole of a compound how mass of a mole of a compound is calculatedis calculated

You often measure the amount of something You often measure the amount of something by one of three different methods — by count, by one of three different methods — by count, by mass, and by volume.by mass, and by volume.

The MoleThe Mole A A molemole is the is the SI unit ofSI unit of countingcounting

A mole equals 6.02 x 10A mole equals 6.02 x 102323 of of anythinganything

602,000,000,000,000,000,000,000602,000,000,000,000,000,000,000 Avogadro’s NumberAvogadro’s Number

Average atomic mass (amu)Average atomic mass (amu) is equal to is equal to molar massmolar mass, the mass of one mole of a , the mass of one mole of a substancesubstance..

Formula weightFormula weight and and molecular weightmolecular weight are the mass of one mole of an ionic and are the mass of one mole of an ionic and molecular compound, respectively.molecular compound, respectively.

The Other MoleThe Other Mole

A mole of any substance contains A mole of any substance contains Avogadro’s number of representative Avogadro’s number of representative particles, or 6.02 particles, or 6.02 10 102323 representative representative particles.particles.

The term The term representative particlerepresentative particle refers to refers to the species present in a substance: usually the species present in a substance: usually atoms, molecules, or formula units.atoms, molecules, or formula units.

Mole ExamplesMole Examples

1 mole of “Vanadium” = 6.02 x101 mole of “Vanadium” = 6.02 x1023 23 atomsatoms

50.941 g of “Vanadium” = 6.02 x1050.941 g of “Vanadium” = 6.02 x1023 23 atomsatoms

1 mole of “Vanadium” = 50.941 g 1 mole of “Vanadium” = 50.941 g

1 mole of “Helium” = 6.02 x101 mole of “Helium” = 6.02 x1023 23 atomsatoms

4.0026 g of “Helium” = 6.02 x104.0026 g of “Helium” = 6.02 x1023 23 atomsatoms

1 mole of “Helium” = 4.0026 g 1 mole of “Helium” = 4.0026 g

# of moles = (2.17 x1023 particles) / (6.02 x 1023

particles/mol)

= 0.360 moles

Moles to Number of ParticlesMoles to Number of Particles

# of “S” atoms = (1.14 mol)(6.02 x 1023 atom/mol) = 6.86 x 1023 atoms

# of “O” atoms = 3 x (1.14 mol)(6.02 x 1023 atom/mol) = 20.6 x 1023 atoms

Total = 6.86 x 1023 + 20.6 x 1023 = 2.75 x 1024 atoms

Mass of a Mole of an ElementMass of a Mole of an Element

Molar massMolar mass is the mass of one mole of is the mass of one mole of an element, expressed in grams/molan element, expressed in grams/mol..

You can find the molar mass of an You can find the molar mass of an element under its atomic symbol on the element under its atomic symbol on the periodic table.periodic table.

The molar mass of carbon, sulfur, mercury, and iron The molar mass of carbon, sulfur, mercury, and iron are shown.are shown.

Converting Grams to MolesConverting Grams to Moles

If given grams, divide by average atomic mass to If given grams, divide by average atomic mass to get moles:get moles:

15 g of “Mo”15 g of “Mo” = 15 g/95.94 g/mole = = 15 g/95.94 g/mole = 0.156 moles0.156 moles

15 g of “H”15 g of “H” = 15 g/1.0079 g/mole = = 15 g/1.0079 g/mole = 14.88 moles14.88 moles

Mass of a Mole of a CompoundMass of a Mole of a Compound

To calculate the molar mass of a compound:To calculate the molar mass of a compound:

1)1) find the number of grams of each element in one find the number of grams of each element in one mole of the compound. mole of the compound.

2)2) then add the masses of the elements in the then add the masses of the elements in the compound.compound.

Use values of molar mass (g/mol) for each Use values of molar mass (g/mol) for each element from the periodic chart. element from the periodic chart.

Thus 1 mol of SOThus 1 mol of SO33 has a mass of 80.1 g. has a mass of 80.1 g.

Molar Masses of Glucose, Water, Molar Masses of Glucose, Water,

and Paradichlorobenzeneand Paradichlorobenzene

P = 30.97 g/mole

Cl = 35.45 g/mole

Molar Mass = 30.97 g + 3 x 35.45 g = 137.33 g

1. Three common ways of measuring the 1. Three common ways of measuring the amount of something are by count, by amount of something are by count, by mass, andmass, and

a)a) by temperature.by temperature.

b)b) by volume.by volume.

c)c) by area.by area.

d)d) by density.by density.

1. Three common ways of measuring the 1. Three common ways of measuring the amount of something are by count, by amount of something are by count, by mass, andmass, and

a)a) by temperature.by temperature.

b)b) by volumeby volume..

c)c) by area.by area.

d)d) by density.by density.

2. A mole of hydrogen gas, H2. A mole of hydrogen gas, H22(g), contains (g), contains

6.02 x 106.02 x 102323

a)a) molecules.molecules.

b)b) atoms.atoms.

c)c) amu.amu.

d)d) grams.grams.

2. A mole of hydrogen gas, H2. A mole of hydrogen gas, H22(g), contains (g), contains

6.02 x 106.02 x 102323

a)a) moleculesmolecules..

b)b) atoms.atoms.

c)c) amu.amu.

d)d) grams.grams.

3. The atomic mass of fluorine is 19.0 amu, 3. The atomic mass of fluorine is 19.0 amu, so the molar mass isso the molar mass is

a)a) 19.0 amu.19.0 amu.

b)b) 19.0 g.19.0 g.

c)c) 6.02 x 106.02 x 102323 amu. amu.

d)d) 6.02 x 106.02 x 102323 g. g.

3. The atomic mass of fluorine is 19.0 amu, 3. The atomic mass of fluorine is 19.0 amu, so the molar mass isso the molar mass is

a)a) 19.0 amu.19.0 amu.

b)b) 19.0 g19.0 g..

c)c) 6.02 x 106.02 x 102323 amu. amu.

d)d) 6.02 x 106.02 x 102323 g. g.

4. Calculate the molar mass of ammonium 4. Calculate the molar mass of ammonium nitrate.nitrate.

a)a) 45.02 g45.02 g

b)b) 80.05 g80.05 g

c)c) 60.06 g60.06 g

d)d) 48.05 g48.05 g

4. Calculate the molar mass of ammonium 4. Calculate the molar mass of ammonium nitrate.nitrate.

a)a) 45.02 g45.02 g

b)b) 80.05 g80.05 g

c)c) 60.06 g60.06 g

d)d) 48.05 g48.05 g