Lect_W4 - General Chemistry CHEM 151 Week 4 UA GenChem Week...

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UA GenChem General Chemistry CHEM 151 Week 4
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UA GenChem Week 4 Reading Assignment See D2L
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UA GenChem Counting Particles Is it practical, in a lab situation, to physically COUNT the particles? NO!! The particles are too small! So – how do we typically measure the amount of a substance we have in a laboratory? We use the MASS to determine the amount of substance. How is mass related to the number of particles?
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UA GenChem Relative Mass and Molar Mass 2.0 g of H 2 22.4 L 18.0 g H 2 O 32.0 g O 2 4 Be 9.012 76 Os 190.23 9 F 19.00 Relative Atomic Mass in atomic mass units (amu) Molar Mass if expressed in grams BY EXPERIMENT Each sample contains AVOGADRO’s Number of particles .
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UA GenChem Molar Mass The mass of one mole of atoms is called the Molar Mass of the element Average Mass (g) = The Molar Mass is the mass of 6.022 x 10 23 of particles of a given substance. 1 mol of C C 6.0221 x 10 atoms of C
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UA GenChem What Makes Them Similar/Different? These are one mole of 6 different substances. If we weigh them, the mass we get is called the “Molar Mass” 6.0221 x 10 23 particles or units in each
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UA GenChem NEWS Where is our exam? Social Sciences 100 When? Mon. sept 22 5 pm – 6:10 What if you have a class then? Can get a piece of paper and take make-up test When do they stop giving tickets to the other exam? End of this week What do you put on the scantron sheet? Look at D2L When is the preceptor review? Where? Wed. 6-8 and thurs. 6-8 in old chem 134
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UA GenChem Quantitative Analysis Central Question How much of a substance do we have? Central concepts Molar Mass 12.01 g Mole 6.0221 x 10 23 units Atomic Mass 12.01 amu C Carbon Atom Microscopic Macroscopic 1/12 weight of 1 atom of C (12) = 1/ 6.022 x10 23 = 1.66 x 10 -24 g
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UA GenChem How many moles of Mg do we have in 0.200 g of Mg? How many atoms in this piece of Mg?
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This note was uploaded on 04/07/2009 for the course CHEM 151 taught by Professor Staff during the Spring '08 term at University of Arizona- Tucson.

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Lect_W4 - General Chemistry CHEM 151 Week 4 UA GenChem Week...

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