# Chemical Quantities 10.1 The Mole: A Measurement of Matter Chapter 10

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Chemical Quantities 10.1 The Mole: A Measurement of Matter Chapter 10

The Mole Concept Avogadro’s Number = 6.022 x 1023 Objectives:
To state the value of Avogadro’s number: x1023. To state the mass of Avogadro’s number of atoms for any element by referring to the periodic table. To relate the moles of a substance to the number of particles. Avogadro’s Number = x 1023

CHEMISTRY & YOU How can you quantify the amount of sand in a sand sculpture? You could measure the amount of sand in a sculpture by counting the grains of sand. Is there an easier way to measure the amount of sand? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Chemical Quantities There are terms used to equate a certain quantity of matter For example 1 dozen = 12, 1 Ton = 2,000 LBs and 1 gross = 144. Before we get to the chemical terms lets convert between units we already know

For example – let’s say you want to buy some Bazooka Gum
You could buy it by the piece from the deli You could buy it by the box from ShopRite You could buy it by mass from the candy store

So, the different ways to measure Bazooka gum
1 dozen = 12 pieces 1 dozen = 1.75 boxes 1 dozen = 168 grams

Based on those conversions, I can determine how much Bazooka gum I have, regardless of how it is measured. I have 95 pieces of Bazooka gum, how many grams do I have?

I have 95 pieces of Bazooka gum, how many grams to I have?

Do-Now If I have 2 stadiums how many baseball bats do I want to purchase? 2 baseball players = 4 baseball bats 1 stadium = 18 baseball players 18 baseball players = 52 corn dogs

What Is a Mole? What Is a Mole? How do chemists count the number of atoms, molecules, or formula units in a substance? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

What Is a Mole? Recall that matter is composed of atoms, molecules, and ions. These particles are much, much smaller than grains of sand, and an extremely large number of them are in a small sample of a substance. Obviously, counting particles one by one is not practical. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Chemical Quantities In chemistry, there are many way to measure the amount of substance The count (quantity) The volume (how much space it takes up) The mass (the amount of matter) Knowing how the count, mass, and volume of an item relate to a common unit allows you to convert among these units.

In chemistry, we do not use a dozen.
Since atoms are so small, we need a quantity with a larger amount We use the mole (mol) 1 mole = X 1023 representative particles (atoms, molecules, formula units) It is known as Avogadro’s number Amedeo Avogadro

Amedeo Avogadro An Italian chemist whose important contributions was his resolution of the confusion surrounding atoms and molecules. Avogadro believed that particles could be composed of molecules and that molecules could be composed of still simpler units, atoms. The number of molecules in a mole (one gram molecular weight) was termed Avogadro's number

We usually are dealing with three types of representative particles
Molecules H2O and H2 are molecules, covalently bonded Atoms Al and Na are atoms, not bonded Formula units CaCl2 and NaOH are formula units, ionicly bonded

1 mole of any representative particle is always 6.02 X 1023
Using this value we can convert between moles and atoms/ molecules/ formula units

For example: If a sample contains 0
For example: If a sample contains mol of O2, how many representative particles are present? 0.476 mol O2 x (6.022 x 1023 particles/1 mol O2) = x 1023

For example: If a sample contains 5
For example: If a sample contains X 1021 atoms of aluminum, how many moles are present?

Converting Number of Atoms to Moles
Sample Problem 10.2 Converting Number of Atoms to Moles Magnesium is a light metal used in the manufacture of aircraft, automobile wheels, and tools. How many moles of magnesium is 1.25 × 1023 atoms of magnesium? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

We can determine the molar mass of representative particles
Molar mass is the mass of 1 mole of that substance The atomic mass is equal to the molar mass for an element 1 mol Na = g Na

For molecules and formula units, we must calculate the molar mass
Let’s calculate the molar mass of SO3 S = 1 X = 32.07 O = 3 X = 48.00 = g/mol

We can use the molar mass of a substance to convert from moles to mass
Remember the molar mass is the mass of 1 mole of that substance SO3 = g/mol = g SO3 1 mol SO3

Using this relationship, we can easily convert a mole amount to a mass amount
How many grams is there in a mole sample of SO3?

We can also convert a mass amount to a mole amount
How many moles is there in a 28.5 gram sample of SO3?

Key Concepts The mole allows chemists to count the number of representative particles in a substance. The atomic mass of an element expressed in grams is the mass of a mole of the element. To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

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