1 The MOLE. 2 Atoms and molecules are very, very small, but we still need to “count” them.

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1 The MOLE

Transcript of 1 The MOLE. 2 Atoms and molecules are very, very small, but we still need to “count” them.

Page 1: 1 The MOLE. 2 Atoms and molecules are very, very small, but we still need to “count” them.

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The MOLE

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Atoms and molecules are very, very small, but we still

need to “count” them.

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The molemole is a

quantity; it is used to

“count” atoms and molecules.

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How we count atoms quickly

We have words that represent numbers that we use everyday.

FOR INSTANCE:– A dozen always = 12 items– A ream of paper always = 500 sheets of

paper– A trio always = 3 of the item.

SO IN CHEMISTRY………..

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…. we have the mole

1 mole = 6.02 x 1023 particles

AND

6.02 x 1023 is called

Avogadro’s number

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1 mole of Al atoms = 6.02 x 1023 Al

atoms1 mole H2O molecules = 6.02 x 1023 H2O

molecules1 mole jelly donuts = 6.02 x 1023 jelly

donuts1 mole of = 6.02 x 1023

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6.02 x 1023 is a VERY large

number

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602,000,000,000,000,000,000,000

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If Kevin took 1 mole of steps, each 15 cm long, he would

walk around the earth 2.26 x 1015 times, which is 2,260,000,000,000,000 or

2,260 trillion times!

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We cannot count

6.02 x 1023 Al atoms, it is just too too many.

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We can, however, measure 26.98 grams

of Al.

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26.98 grams of Al contains 6.02 x 1023 Al

atoms!

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26.98 grams of Al contains 1 mole of Al

atoms!

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The formula weight of any substance = mass of 1 mole of that substance in grams.

(26.98 grams is the formula weight of Al.)

So 26.98 grams of Aluminum is ONE mole of Aluminum.

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The formula weight of any element is the weight of an atom/molecule expressed in amu’s.

(26.98 amu is also the atomic mass of Al)

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More about amu

While amu is a valid unit for expressing weights of atoms and molecules, we are not going to be using it that often.

The reason is that it is the mass of a single unit and we are not able to use a single unit, since it is too small.

Know the definition of amu and all is well.

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The formula weight of any compound is the sum of the formula weights of all the atoms in that compound, expressed in grams.

(The formula weight of H2O = 18 grams per mole. (g / n ))

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Identical Terms The following terms on the next slide are often

interchangeable . – All can be expressed in grams or amu depending on

the application.– The term mass or weight is also often

interchangeable. Since all of our calculations will be done on Planet Earth, the gravity is constant so we can make this simplification.

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Here are the terms. Formula weight: The most general of all the

terms on this list. Atomic weight (or mass): The weight of a mole

of a single element. Molecular weight (or mass): The weight of a

mole of a single compound. Molar mass: The weight of one mole of

material. Just a rephrasing of above.

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Molar conversions: The magic formula

Mass in grams of an element or compound divided by molar mass = number of moles.

We can make this into a formula and this is without a doubt the

MOST IMPORTANT FORMULA

IN CHEMISTRY.

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The MAGIC FORMULA

The formula referred to on the earlier slide is:

Moles = Grams / Formula Weight OR

n = g / M

This is not a formula –

This is THE FORMULA !!

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Quantity conversions: Moles to number of particles

Number of atoms or molecules divided by Avogadro’s number = number of moles.

Set up a proportion !!

We can all cross-multiply

1 mole = x moles

6.02 x 1023 y particles

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PracticeFill out the following table in your notebook.

Number of particles Moles

4.56 x 1025 ___________

7.66 x 1022 ___________

_____________ .234

_________ 34.56

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Practice AnswersFill out the following table in your notebook.

Number of particles Moles

4.56 x 1025 75.75

7.66 x 1022 .127

1.41 x 1023 .234

2.08 x 1025 34.56

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Moles to Liters

If the material is a gas, we can use the fact that 1 mole of gas = 22.4 Liters to find its volume.

We should set up a proportion. 1 mole = x moles

22.4 L y Liters

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Subscripts in chemical formulas can help us represent moles!

Since 1 molecule of CO2 contains 1 atom of C and 2 atoms of O, then…

1 dozen molecules of CO2 contain 1 dozen atoms of C and 2 dozen atoms of O, and…

1 mole CO2 contains 1 mole C and 2 moles O !

This is a very useful relationship.

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Molarity

Concentration of a solution, i.e. the amount of solute that is dissolved in a given amount of solvent

number of moles of solute per liter of solution

Units = mol/L OR n / L

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Percent Composition Percent that each part of a substance is of the

whole, by mass. The whole mass is always the formula weight !

The sum of the percents must = 100 % % part = (mass of part / mass of whole) x 100 % The percent composition of CO2 is as follows…

Wt. of C = 12g Wt. of O = 16g FW = 44 g

% C = (12 / 44) x 100 % = 27.27 %

% O = ((2 x 16 ) / 44) x 100 % = 72.73 %

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Empirical Formula

Formula expressing the simplest whole number ratio of atoms in a compound

The empirical formula is often not the TRUE formula.

It is used to identify a compound in situations like forensics or learning about a new compound.

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More on Empirical Formula C6H12O6 has an empirical formula CH2O

Found by calculating the ratio of the moles of each element in the compound.

STEPS (also found on the website)– Convert each given to number of moles.

Assume a 100 gram sample if needed.

– Divide by the lowest number of moles to get a ratio.– Manipulate the values so they are whole numbers.

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Molecular Formula Determining the True or Actual Formula of the

compound. The empirical formula is needed first. The weight of the molecular formula is given.

– It will always be a multiple of the empirical formula.

The molecular formula is a multiple of the empirical formula.

CH2 is the empirical formula for all of the following: C2H4 C3H6 C4H8 C6H12 and many more


The Mole Ch.8. (8-1) Mole (mol): amt. of substance – # of atoms in 12g of carbon-12 Avogadro’s constant: 6.02 x 10 23 particles / mol –Atoms, molecules.

The Mole Ch.8. (8-1) Mole (mol): amt. of substance – # of atoms in 12g of carbon-12 Avogadro’s constant: 6.02 x 10 23 particles / mol –Atoms, molecules.

The Mole - crispyteacher.weebly.com · introduced the mole concept in the ... •Keep in mind that Avogadro’s number is ... MOLE MAP MassMoles Molecules Atoms Mult by MM

The Mole - crispyteacher.weebly.com · introduced the mole concept in the ... •Keep in mind that Avogadro’s number is ... MOLE MAP MassMoles Molecules Atoms Mult by MM

The Mole - Weebly€¦ · mole Avogadro’s number • Main Idea - Chemists use the mole to count atoms, molecules, ions, and formula units. • NOTE –YOU WILL NEED A SCIENTIFIC

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Avogadro’s Number and the Mole Atoms, ions, and molecules are very small, so even tiny samples have a huge number of particles. To make counting such.

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Atoms, Moles, And the Mole Concept

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What Is a Mole?. One mole = 6.022 x 10 23 items A mole of atoms Or molecules.

What Is a Mole?. One mole = 6.022 x 10 23 items A mole of atoms Or molecules.

Chemists need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance. MOLE The Mole:

Chemists need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance. MOLE The Mole:

THE MOLE Chapter 10. 10.1 MEASURING MATTER 1.Chemists use the mole to count atoms, molecules, and ions. 1. Atoms – individual atoms 2. Molecules – two.

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WHAT IS A MOLE?. Moles: Measuring Matter A UNIT OF MEASURE!!! 1 mole = 6.02 x 10 23 representative particles – atoms, molecules, formula units, ions –

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Stoichiometry Chemistry Dr. May. Moles One mole of anything contains Avogadro’s number of particles: One mole of sodium (Na) contains 6.02 x 10 23 atoms.

Stoichiometry Chemistry Dr. May. Moles One mole of anything contains Avogadro’s number of particles: One mole of sodium (Na) contains 6.02 x 10 23 atoms.

1 · Web view1.1 Mole Concept and Avogadro's Constant Describe the mole concept and apply it to substances. The mole concept applies to all kinds of particles: atoms, molecules, ions,

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Mole concept - Grey College, Bloemfontein · 2020-04-14 · Mole concept. There are 6,02 x 1023 atoms in 12 g of carbon-12. Avogadros constant (N A) 1 Mole is the amount of substance

Mole concept - Grey College, Bloemfontein · 2020-04-14 · Mole concept. There are 6,02 x 1023 atoms in 12 g of carbon-12. Avogadros constant (N A) 1 Mole is the amount of substance

The Mole - Oak Park Independent Notes.pdfThe Mole • A mole is a unit used to measure amount of atoms, molecules, ions, etc. (particles that are very small, but can be applied to

The Mole - Oak Park Independent Notes.pdfThe Mole • A mole is a unit used to measure amount of atoms, molecules, ions, etc. (particles that are very small, but can be applied to

The Mole Chapter 8.2 What is a mole? It is "that equal number" of atoms arbitrarily chosen. the number of atoms in the atomic weight in g of any.

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Atomic Masses & the MOLE…. Masses of atoms expressed in grams are extremely small.Masses of atoms expressed in grams are extremely small. –An atom of.

Atomic Masses & the MOLE…. Masses of atoms expressed in grams are extremely small.Masses of atoms expressed in grams are extremely small. –An atom of.

Basic Chemistry Atoms, Elements & Molecules. Atoms Around Us “To understand the very large, we must understand the very small” Democritus Atoms Atomos.

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Atoms and Molecules - teamtoler.weebly.com · Atoms and Molecules Symbols and Formula Masses of Atoms and Molecules The Atom Isotopes The Mole Chemical Formula Atomic Symbols •Each

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Mole Concept - Resonance DLPD€¦ · Mole is a chemical counting S unit and defined as follows : A mole is the amount of a substance that contains as many entities (atoms, molecules

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