151F09_W4_LV_3 - General Chemistry CHEM 151 Week 4 UA...

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UA GenChem General Chemistry General Chemistry CHEM 151 CHEM 151 Week 4
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UA GenChem Differentiating Particles How can we start differentiating what types of particles we have in a given substance? Equal volumes of gas under the same P and T have the same number of particles . H 2 O 2 If we find that 10 L of O 2 are 16 times heavier than 10 L of H 2 , What can we conclude? PV = nRT
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UA GenChem Counting Particles Counting Particles Is it practical, in a lab situation, to Is it practical, in a lab situation, to physically physically COUNT COUNT the particles? the particles? NO!! The particles are too small! So – how do we typically measure the So – how do we typically measure the amount of a substance we have in a amount of a substance we have in a laboratory? laboratory? We use the MASS to determine the amount of substance. How is mass related to the number How is mass related to the number of particles? of particles?
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UA GenChem 2 He 4.003 18 Ar 39.95 10 Ne 20.18 Relative Mas s By comparing the mas s es of equal volumes of different gas es , it is pos s ible to calculate the relative mas s es of their particles : Standard Temperature and Pres s ure STP T = 0 o C = 273.15 K and P = 1.00 atm 4.0 g of He 22.4 L 20.18 g Ne 22.4 L 39.95 g Ar 22.4 L Relative Mas s 6.022 x 10 23 particles in all of them
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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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GenChem Molar Mass Molar Mass The mass of one mole of atoms is The mass of one mole of atoms is called the Molar Mass of the element called the Molar Mass of the element Average Mass Average Mass (g) (g) = = Molar Mass Molar Mass The Molar Mass is the mass of The Molar Mass is the mass of 6.022 x 6.022 x 10 10 23 23 of particles of a given substance.
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151F09_W4_LV_3 - General Chemistry CHEM 151 Week 4 UA...

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