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**Moles, Avogadro’s Number and Molar Mass**

Converting moles to molecules, atoms, and particles

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**Can anyone define the term mole?**

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**Mole SI unit used to measure the amount of a substance**

equal to 6.02 x 1023 atoms, molecules, or particles Avogadro’s number Abbreviated by mol

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**Avogadro’s Number 6.02 X 1023 Used to count extremely small particles**

Named in honor of Italian physicist Amedeo Avogardo Determined the volume of one mole of a gas

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Conversions

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**Mole Molecules, Atoms, or Particles**

In order to convert moles to molecules atoms, or particles, you have to MULTIPLY the number of moles by Avogadro’s number (6.02 x 1023) Example: How many atoms are there in 4.0 moles?

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**How many atoms are there in 4.0 moles?**

Moles Atoms…MULTIPLY BY AVOGADRO’S NUMBER 2.4 x 1024 atoms

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**Molecules, Atoms, or Particles Moles**

In order to convert molecules, atoms, or particles to moles, you have to DIVIDE the number of moles by Avogadro’s number (6.02 x 1023) Example: How many moles are there in 7.14 x 1023 molecules?

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**How many moles are there in 7.14 x 1023 molecules?**

Molecules Moles…DIVIDE BY AVOGADRO’S NUMBER 1.19 moles

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Practice

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**How many molecules are there in 3.5 moles?**

Moles Molecules…MULTIPLY BY AVOGADRO’S NUMBER 2.11 x 1024 molecules

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**How many particles are there in 9.6 moles?**

Moles Particles…MULTIPLY BY AVOGADRO’S NUMBER 5.78 x 1024 particles

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**How many moles are there in 5.75 x 1024 atoms?**

Atoms Moles…DIVIDE BY AVOGADRO’S NUMBER 9.55 moles

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**How many moles are there in 3.58 x 1023 particles?**

Molecules Moles…DIVIDE BY AVOGADRO’S NUMBER 0.59 moles

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End Day 1

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Molar Mass

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**Molar Mass the mass in grams of one mole of any pure substance**

In other words, the molar mass of any element is equivalent to the atomic mass of that element in units of grams per mole; g/mol

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**Calculating Molar Mass**

- To calculate the molar mass of a substance, you add the atomic mass of every element in the compound The total atomic mass is the molar mass of the substance.

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**What is the molar mass of N?**

Example What is the molar mass of N? Step 1: determine the atomic mass N: 14 Step 2: add units g/mol molar mass = 14 g/mol

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**What is the molar mass of CO2?**

Example What is the molar mass of CO2? Step 1: determine the mass of each element C: 12 O: 16 X 2 Step 2: add the masses to get the total atomic mass =44 Step 3: add units g/mol Molar mass = 44 g/mol

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**Practice What is the molar mass of NaCl?**

58.5 g/mol What is the molar mass of H3O? 19 g/mol What is the molar mass of H2SO4? 98 g/mol

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END

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**Mole Gram Conversions**

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Review Mole SI unit used to measure the amount of a substance Abbreviate by mol Molar mass total atomic mass of every element in the compound Units: g/mol

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**What is the molar mass of NH3?**

Step 1: determine the mass of each element N: 14 H:1 X 3 Step 2: total the masses 14+3=17 Step 3: attach the units 17g/mol

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**Mole Gram Conversions**

When given the number of moles, MULTIPLY by the molar mass of the substance. What is the mass of 5 moles of H2O?

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**What is the mass of 5.O moles of H2O?**

Step 1: Write the given Step 2: Multiply by molar mass Step 3: Cancel the units Step 4: Solve 90 grams H2O

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**Gram Mole Conversions**

When given the number of moles, DIVIDE by the molar mass of the substance. How many moles are equivalent to 50g N?

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**How many moles are equivalent to 50g N?**

Step 1: Write the given Step 2: Divide by the molar mass Step 3: Cancel the units Step 4: Solve 3.57 moles N

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Practice

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**What is the mass of … 2.22 mol Ti 1.22 X 1023 mol Ag 4.5 mol H2SO4**

106 g Ti 1.22 X 1023 mol Ag 1.32 X 1025 g Ag 4.5 mol H2SO4 441 g H2SO4

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**How many moles are consumed in…**

5.62 g Kr mol Kr 55 g As 0.73 mol As 7.5 g NaCl 0.128 mol NaCl

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End Day 2

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**Particles Gram Conversions**

Remember, particles, atoms, and molecules are all the same To convert particles to grams… 1st: convert particles to moles 2nd: convert moles to grams

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Review When converting from moles to atoms, molecules, or particles, you must MULTIPLY by Avogadro’s number. When converting atoms, particles, or molecules to moles, you must DIVIDE by Avogadro’s number.

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**What is the mass of 2.5 X 1023 atoms of H2O?**

Step 1: convert atoms to moles Step 2: convert moles to grams

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**Grams Particles Conversions**

Once again, remember particles, atoms, and molecules are all the same To convert grams to particles… 1st: grams to moles 2nd: convert moles to particles

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**How many molecules are in 4.5 g C?**

Step 1: Convert grams to moles Step 2: Convert moles to molecules

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**Practice How many grams are in 5.0 X 1024 atoms of K?**

What is the mass of 8.5 X 1023 molecules of NH2? How many particles are in 3.75 g Ca? How many molecules are in 96 g HBr2?

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Practice On your own, work pg. 347:

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