Chapter 6.pptx

# Chapter 6.pptx - Chapter 6 Chemical Composition How much is...

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Chapter 6 Chemical Composition How much is more important than why.

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Moles
Moles The unit used to count atoms is the mole. A mole has the value of 6.022 x atoms. 1 mol = 6.022 x

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Moles 6.022 x is called Avogadro’s number. It is named for Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto.
Moles One mole of anything is 6.022 x units of that thing. The numerical value of the mole is defined as the number of atoms in exactly 12 grams of pure carbon-12.

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Moles Using the fact that one mole is always equal to 6.022 x gives you a conversion factor. or
Converting moles to # of atoms If you have 3.5 moles of He how many atoms of He do you have?

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Converting moles to # of atoms If you have 3.5 moles of He how many atoms of He do you have? 3.5 moles of He x = 2.1 x atoms
Molar Mass The mass of 1 mole of atoms of an element is its molar mass.

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Molar Mass The mass of 1 mole of atoms of an element is its molar mass. The value of an elements molar mass in grams per mole is numerically equal to the elements atomic mass in atomic mass units.
Example The atomic mass of Si is 28.09 amu.

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Example The atomic mass of Si is 28.09 amu. The molar mass of one mole of Si is 28.09 .
Why? Avogadro’s number is defined as the number of atoms in exactly 12 grams of carbon-12.

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Why? Avogadro’s number is defined as the number of atoms in exactly 12 grams of carbon-12. The atomic mass unit is defined at of the mass of a carbon-12 atom.
Why? Avogadro’s number is defined as the number of atoms in exactly 12 grams of carbon-12. The atomic mass unit is defined at of the mass of a carbon-12 atom. Put this together and you get that the atomic mass of one atom of an element in amu is equal the molar mass in

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Mass and Moles Conversions Two step process. 1) Establish the molar mass of the substance. 2) Use the molar mass as a conversion factor .
Example How many moles are in 2.35 grams of Ca?

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Example How many moles are in 2.35 grams of Ca?

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