Avogadro's Number Ppt

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A scientific theory named after a rodent. The mole is a unit of that was first described by Amedeo Avogadro Similar idea to “a dozen of eggs” or a “ream of paper” A mole of substance is equal to 6.02 X 1023 (Avogadro’s number) molecules of any substance. The mass of Avogadro’s number of animal-moles is equal to more than 60 times the combined mass of Earth’s oceans. If spread over the entire surface of Earth, Avogadro’s number of animal-moles would form a layer more than 8 million animal-moles thick. The same number of atoms as any other element meeting the same requirement. 3 The number of atoms in any given element is known as Avogadro's number and has been determined to be equal to 6.02 x 1023 4 Avogadros Number The atomic weight of any element that is being expressed in grams contains 6.02 x 1023 atoms of the element.

The Mole

Slide 2

Avogadro's Number Perrin

CA Standards

Slide 3

The Mole

1 dozen =

1 gross =

Number

1 ream =

1 mole =

12

144

500

6.02 x 1023

There are exactly 12 grams of carbon-12 in one mole of carbon-12.

Slide 4

Avogadro’s Number

6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855).

Amadeo Avogadro

I didn’t discover it. Its just named after me!

Slide 5

Calculating Formula Mass

Calculate the formula mass of carbon dioxide, CO2.

12.01 g + 2(16.00 g) =

44.01 g

What Is Avogadro's Number

 One mole of CO2 (6.02 x 1023 molecules) has a mass of 44.01 grams

Slide 6

Mole Relationships

Mole

Atoms

or molecules

Liters

Grams

6.02 x 1023

Atomic

Mass

22. 4 L

22.4

Avogadro

L

Slide 7

Calculations with Moles: Converting moles to grams

How many grams of lithium are in 3.50 moles of lithium?

Avogadro's Number Practice

3.50 mol Li

= g Li

1 mol Li

6.94 g Li

24.3

Slide 8

Calculations with Moles: Converting grams to moles

How many moles of lithium are in 18.2 grams of lithium?

18.2 g Li

= mol Li

6.94 g Li

1 mol Li

2.62

Slide 9

Calculations with Moles: Using Avogadro’s Number

How many atoms of lithium are in 3.50 moles of lithium?

3.50 mol

= atoms

1 mol

6.02 x 1023 atoms

2.07 x 1024

Slide 10

Calculations with Moles: Using Avogadro’s Number

How many atoms of lithium are in 18.2 g of Auto transmission.

lithium?

18.2 g Li

= atoms Li

1 mol Li

6.022 x 1023 atoms Li

1.58 x 1024

6.94 g Li

1 mol Li

(18.2)(6.022 x 1023)/6.94

Avogadro

Slide 11

Standard Molar Volume

Equal volumes of all gases at the same temperature and pressure contain the same number of molecules.

- Amedeo Avogadro

At STP (Standard Temperature and Pressure):

1 mole of a gas occupies 22.4 liters of volume

Slide 12

Calculations with Moles: Using Standard Molar Volume

Learning Objective

  • Define and memorize Avogadro’s number

Key Points

  • The mole allows scientists to calculate the number of elementary entities (usually atoms or molecules) in a certain mass of a given substance.
  • Avogadro’s number is an absolute number: there are 6.022×1023 elementary entities in 1 mole. This can also be written as 6.022×1023 mol-1.
  • The mass of one mole of a substance is equal to that substance’s molecular weight. For example, the mean molecular weight of water is 18.015 atomic mass units (amu), so one mole of water weight 18.015 grams.

Term

  • moleThe amount of substance of a system that contains as many elementary entities as there are atoms in 12 g of carbon-12.

The chemical changes observed in any reaction involve the rearrangement of billions of atoms. It is impractical to try to count or visualize all these atoms, but scientists need some way to refer to the entire quantity. They also need a way to compare these numbers and relate them to the weights of the substances, which they can measure and observe. The solution is the concept of the mole, which is very important in quantitative chemistry.

Avogadro’s Number

Amadeo Avogadro first proposed that the volume of a gas at a given pressure and temperature is proportional to the number of atoms or molecules, regardless of the type of gas. Although he did not determine the exact proportion, he is credited for the idea.

Avogadro’s number is a proportion that relates molar mass on an atomic scale to physical mass on a human scale. Avogadro’s number is defined as the number of elementary particles (molecules, atoms, compounds, etc.) per mole of a substance. It is equal to 6.022×1023 mol-1 and is expressed as the symbol NA.

Avogadro’s number is a similar concept to that of a dozen or a gross. A dozen molecules is 12 molecules. A gross of molecules is 144 molecules. Avogadro’s number is 6.022×1023 molecules. With Avogadro’s number, scientists can discuss and compare very large numbers, which is useful because substances in everyday quantities contain very large numbers of atoms and molecules.

The Mole

The mole (abbreviated mol) is the SI measure of quantity of a “chemical entity,” such as atoms, electrons, or protons. It is defined as the amount of a substance that contains as many particles as there are atoms in 12 grams of pure carbon-12. So, 1 mol contains 6.022×1023 elementary entities of the substance.

Chemical Computations with Avogadro’s Number and the Mole

Avogadro’s number is fundamental to understanding both the makeup of molecules and their interactions and combinations. For example, since one atom of oxygen will combine with two atoms of hydrogen to create one molecule of water (H2O), one mole of oxygen (6.022×1023 of O atoms) will combine with two moles of hydrogen (2 × 6.022×1023 of H atoms) to make one mole of H2O.

Another property of Avogadro’s number is that the mass of one mole of a substance is equal to that substance’s molecular weight. For example, the mean molecular weight of water is 18.015 atomic mass units (amu), so one mole of water weight 18.015 grams. This property simplifies many chemical computations.

If you have 1.25 grams of a molecule with molecular weight of 134.1 g/mol, how many moles of that molecule do you have?

[latex]1.25g times frac{ 1 text{ mole}}{134.1g}=0.0093 text{ moles}.[/latex]

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Avogadro's Number Physics

http://www.chem1.com/acad/webtext/intro/int-2.html#SEC2
Steve Lower’s Website
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http://en.wiktionary.org/wiki/mole
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Avogadro's Full Number

http://en.wikipedia.org/wiki/Mole_(unit)
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http://en.wikipedia.org/wiki/Avogadro_constant
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