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Avogadro’s Number Mole Molar Mass
Measuring Matter Avogadro’s Number Mole Molar Mass
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How Scientists Keep Track of Atoms
A ream of paper is 500 sheets: 1 ream = 500 sheets A counting unit appropriate for objects based on their size/function Always constant Easier to sell by ream than by sheet Scientist could count atoms Atoms are extremely small The number of individual particles even in a small sample is REALLY SMALL!
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The Mole A ‘chemical’ counting unit SI base unit
Measures amount of a pure substance Abbreviated ‘mol’ Scientist developed One mole contains Avogadro’s number of particles This number is named in honor of Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter the identity of the gas, there were the same number of molecules present
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How much is the mole? Similar to a dozen except instead of 12,
A mole = or 6.02 x 1023 = Avogadro’s Number. It is equal to that number no matter what kind of particles: Atoms Molecules Formula unit
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How Do We Use The Mole? We’d never use the mole to describe macroscopic or real world objects. 1 mole (6.02x1023) of watermelon seeds would be found inside a watermelon the size of the moon. 1 mole (6.02x1023) of donut holes would cover the earth and would be 5 miles deep.
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How do we use the mole? Mole is a huge number of particles
only used to describe the amount of things that are very, very small. 1 mole (6.02x1023) of water molecules would barely fill a shot glass
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A Mole of Particles Contains 6.02 x 1023 particles
= 6.02 x 1023 C atoms = 6.02 x 1023 H2O molecules = 6.02 x 1023 NaCl formula units 1 mole C 1 mole H2O 1 mole NaCl
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Avogadro’s Number as Conversion Factor
6.02 x 1023 particles 1 mole or 1 mole Note: a particle could be an atom, a molecule or a formula unit
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Practice How many moles of silver are in 3.01x1023 atoms of silver?
Given: 3.01 x 1023 atoms Ag Find: Moles of Ag 6.02x1023 atoms = 1 mol Ag 3.01x1023 Ag atoms 1 mol Ag 6.02x1023 Ag atoms = 0.500mol Ag = 0.5 mol Ag
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Molar Mass The mass of one mole of a pure substance UNIT: (g/mol)
Equal to the numerical value of the average atomic mass (PT) 1 mole of C atoms = g 1 mole of Mg atoms = g 1 mole of Cu atoms = g
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Other Names Related to Molar Mass
Molecular Mass/Molecular Weight Formula Mass/Formula Weight: THE POINT: You may hear all of these terms which mean the SAME Number from the periodic table!!
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Learning Check! = 79.90 g 1 mole of Br 1 mole of Sn = 118.71 g
Find the molar mass = g 1 mole of Br 1 mole of Sn = g Learning Check!
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Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = 1 mole Ca x g/mol + 2 moles Cl x g/mol = g/mol 1 mole of N2O4 g CaCl2 = g
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Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 =
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Learning Check! Molar Mass of K2O = ______ g/mol
Molar Mass of N2O4 = _______g/mol Molar Mass of H20 = ______ g/mol
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Calculations with Molar Mass
Grams Moles Calculations with Molar Mass
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Practice 9.60 mol Al G: F: 1 mol Al = 26.98 g g of Al
Aluminum is often used for the structure of light- weight bicycle frames. How many grams of Al are in 9.60 moles of Al? G: F: 9.60 mol Al 1 mol Al = g g of Al
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Practice G: F: 9.60 mol Al 1 mol Al = 26.98 g g of Al 9.60 mol Al
Aluminum is often used for the structure of light- weight bicycle frames. How many grams of Al are in 9.60 moles of Al? G: F: 9.60 mol Al 1 mol Al = g g of Al 9.60 mol Al 26.98 g Al = 259 g Al 1 mol Al
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Practice Propane gas is needed to operate gas grills. Your father used grams of propane to grill burgers over the weekend. How many moles of propane did he use up? Propane = C3H8 G: F: 110.6 g C3H8 1 molC3H8 = g mol of C3H8
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Practice Propane gas is needed to operate gas grills. Your father used grams of propane to grill burgers over the weekend. How many moles of propane did he use up? Propane = C3H8 G: F: 110.6 g C3H8 1 molC3H8 = g mol of C3H8 110.6 gC3H8 1 mol C3H8 = mol C3H8 44.11 g C3H8
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Calculations using Molar Mass & Avogadro’s Number
Remember: There may not always be a direct pathway to the final answer!! molar mass Avogadro’s number Grams Moles particles Calculations using Molar Mass & Avogadro’s Number
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The TWO Step – I Work it Out!!
How many atoms of Cu are present in 35.4 g of of copper? 1 mol Cu = g G: F: 35.4 g Cu 1 mol Cu = 6.02 x 1023 atoms atoms of Cu 35.4 g Cu 1 mol Cu 6.02 x 1023 atoms Cu 63.55 g Cu 1 mol Cu = 3.35 X 1023 atoms Cu molar mass Avogadro’s number Grams Moles particles
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The TWO Step – I Work it Out!!
How many atoms of Cu are present in 35.4 g of of copper? 1 mol Cu = g G: F: 35.4 g Cu 1 mol Cu = 6.02 x 1023 atoms atoms of Cu molar mass Avogadro’s number Grams Moles particles
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Learning Check! What is the mass (in grams) of 1.20 X molecules of glucose (C6H12O6)? molar mass Avogadro’s number Grams Moles particles
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Now you work it out! How many atoms of O are present in 78.1 g of oxygen? 78.1 g O2 1 mol O X 1023 molecules O2 2 atoms O g O mol O molecule O2
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