MondayNovember 26, 2012

(Discussion and Worksheet – Moles and

Molar Mass)

Bell RingerMonday, 11-26-12

it’s a small burrowing mammal

What is a “mole?”

Bell Ringer Monday, 11-26-12

What is a “mole?”

it’s a skin blemish

Bell Ringer Monday, 11-26-12

What is a “mole?”it’s a spicy sauce

Bell Ringer Monday, 11-26-12

What is a “mole?”

... and it’s also a unit of

measurement used in chemistry to

express amounts of a chemical substance.

Last six-weeks I was very lenient concerning turning in late worksheets and remediating Quizzes well past their “last days.”

Also, as you may have noticed, students were allowed to retake quizzes after they had been released back to their owners.

Merry Christmas!

Here are the new policies for this six-weeks, and there can be no exceptions (sorry):

Formatives (worksheets, labs, daily grades, etc.)

These must be turned in by Friday of the week they are given to you. No worksheets will be given to you after Tuesday of any week. No late turn-

ins and no remediations.

Summatives (Quizzes and Projects)

These must be remediated no later than two weeks after the grade appears in Gradespeed. If you miss a Quiz due to absence, it must be

taken by 5:00 on your second day back in class. Otherwise, it will count as a remediation with a maximum grade of 90. Quiz remediations will

involve a different Quiz from the original one.

Announcements

Assignment Currently Open

Summative or Formative? Date Issued Date Due Date Into

GradeSpeed Final Day

QUIZ 11 S1 11/9 11/9 11/30

QUIZ 12 S2 11/16 11/16 12/7

What is a “mole?”A mole is defined

as an amount of a substance that

contains as many elementary entities (e.g., atoms, molecules, ions, electrons) as there are atoms in 12 grams of

pure carbon-12, the isotope of car

bon with an atomic mass of 12 amu.

QuestionsHow many eggs are in a dozen

eggs?How many roses are in a dozen

roses?How many donuts

are in a dozen donuts?

12

12

12

A DozenA “dozen”, therefore, is a term

we use to designate 12 of anything.

QuestionsHow many pennies

are in a mole of pennies?

How many marshmallows are in

a mole of marshmallows?

How many water molecules are in a

mole of water molecules?

6.022 x 1023

6.022 x 1023

6.022 x 1023

A MoleA “mole”, therefore, is a term we use to designate 6.022 x

1023 of anything.

A MoleBy the way, if you had a mole of

marshmallows, it would cover the surface of the continental United States to a depth of 1170 miles.

A MoleHere’s another way to try to grasp the

enormity of this number.If you split a mole of dollars between

every man, woman, and child on Earth, each would get $86 340 000

000 000.That’s 86 trillion dollars each!In case you’re

curious, each person would get about 100 times more US dollars

than are currently in existence.

The MoleIn chemistry, the “mole” is the standard unit

that indicates the amount of substance present.

A mole is the amount of a substance that contains as many particles as there are atoms in exactly 12g of the carbon-12 isotope, which is:

6.0221367 x 1023.or, 602 213 670 000 000 000 000 000.

Ex.) 12g of the C-12 isotope contains 6.0221367 x 1023 C-12 atoms.

This is Avogadro’s Number – the number of particles in exactly one mole of a pure

substance.

This number can always be reduced and rounded to the correct number of significant figures.

Molar MassThe mass of one mole of a

pure substance is called the molar mass of that

substance.A molar mass of an element contains one mole of atoms.

Ex.) 4.00g of He, 6.946 of Li and 200.59g of Hg all contain

a mole of atoms.

Moles and Molar MassA mole is the amount of a substance that

contains an Avogadro’s number of particles.

What is the approximate mass of one mole of helium atoms? - 4.00 g.

The mass of one mole of a pure substance is called the molar mass of that substance.

Molar mass is usually written in units of g/mol.

Moles and Molar Mass

Sample ProblemTo two decimal places, what is the relative atomic mass and the molar mass of the element chlorine, Cl?

If we consult the Periodic Table, we find that the relative atomic mass of chlorine is 35.45 amu.

Therefore, the molar mass of chlorine is 35.45 grams/mole.

This means that the mass of a mole of chlorine atoms is 35.45 grams, and that

mole contains 6.022 x 1023 chlorine atoms.

Determine the mass in grams of the following:

Moles and Molar Mass

Sample Problem

3.00 mol of sulfurOn the Periodic Table, the mass number of

sulfur is 32.07 amu.Therefore, sulfur’s molar mass is 32.07

g/mol.If there are 32.07 grams of mass in one

mole of sulfur, there are three times that much mass in three moles.

3.00 moles S x 32.07 g/mol = 96.21 g S

Determine the mass in grams of the following:

3.01 x 1023 atoms of fluorineThere is no direct conversion from number of atoms to mass in grams. You must first convert atoms to moles,

then moles to grams.

Moles and Molar Mass

Sample Problem

3.01 x 1023 atoms FX

1

=

atoms F

mol F

g F

1

9.50

Xmol f1

g F19.0

6.02 x 1023

Worksheet

Moles and

Molar Mass