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The sum of the atomic masses of all the atoms in a molecule.
Molecular Weight
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What is the molecular weight of CO2?
CO2: 1 C (12.01 amu) + 2 O (2 x 16.00 amu) = 44.01 amu
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The number of atoms in exactly 12 g of 12C. Number of atoms in 1 atomic mass of an element in grams.
A mole (abbreviated: mol)
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Avogadro’s number of atoms
6.022 x 10E23
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A _________ of anything always represents 6.022 x 1023 of that thing.
Mole
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What is one mole of an element?
- The atomic mass expressed in grams; different for each element.
- ex. 1 mole of Na = mass of 22.99 g, 1 mole of Si = mass of 28.09 g.
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How many Na atoms are there in 5 moles of Na?
- A conversion factor between mass and numbers of things
- (allows us to count atoms by weighing)
- 5 moles Na x 6.022 x 10E23/1 mole Na
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What is the mass of one sodium atom?
22.98 23 amu
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What is the mass of one mole of sodium atoms?
23 grams
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2 moles of sodium contains how many sodium atoms?
2 x 6.002 = 1.204 x 10E24
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How many total atoms are there in one molecule of dinitrogen pentoxide
N2O5 = 7 atoms
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How many atoms are there in 1 mole of dinitrogen pentoxide?
7 x 6.002 = 42.154 = 4.22 x 10E24 atoms
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What is the proper unit for molar mass?
g/mol
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What is the molar mass of oxygen?
O2, 1-O = 15.99, O = 16g, O x 2 = 32g, Answer: 32.00g/mol
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Calculate the molar mass of sodium chloride.
NaCl, Na = 22.989 Cl = 35.452, 23 so 23.00 + 35.45 = 58.45g/mol
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What is the molar mass of calcium hydroxide?
Ca(OH)3, Ca = 40.08, H = 1.01 x 2 = 2.02, O = 16.00 x 2 = 32.00, add all to = 74.10g/mol
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A sample of carbon dioxide has a mass of 220.05 grams. How many moles of carbon dioxide are present in the sample?
C = 12.01 x 1, O = 16.00 x 2 = 32.00, adds up to 44.00. 220.05g/ 44 = 5 moles.
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_____________ compounds chemical formula represents a _____________ unit
Molecular, discrete molecular (e. g. CO2)
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_____________ compounds chemical formula represents a _____________ unit
Ionic, formula (the whole number ratio of cations to anions; e. g. K2SO4)
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The mass of one mole (6.022 × 1023 molecules or formula units) is referred to as the ________ ______ of the compound
molar mass, (formula mass expressed in grams) ex: 44.0 g of CO2 = molar mass of CO2 and is the mass of 6.022 × 10E23 molecules of CO2
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_______ ____________ is the number of moles of each of the elements that make up the compound
Mole composition, CO2 - one mole of C and two moles of O
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________ ____________ is the mass of each element in the compound
Mass composition, CO2 = 12.0 g of C and 32.0 g of O
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Percent composition of a compound
- Mass of each element represented as a percentage of the mass of the entire compound
- Ex: 100 g of NH3, there are 82.0 g of N therefore, the mass percentage of N is 82.0% N
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Chemical formula - _____________ _______Indicates the number of moles of atoms of each element present in one mole of a substance.
Macroscopic View, In one mole of P2O5, two moles of phosphorus and five moles of oxygen are present.
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Chemical formula - _____________ _______ the numerical subscripts in a chemical formula give the number of atoms of the various elements present in 1 formula unit of the substance.
Microscopic View, In one molecule of P2O5, two atoms of phosphorus and five atoms of oxygen are present.
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Which of the following is closest to the average mass of one atom of copper? a. 63.55 g b. 52.00 g c. 58.93 g d. 65.38 g e. 1.055 x 10E-22 g
e. 1.055 x 10E-22, 63.55g divided by 6.022 x 10E23 = 1.055 x 10E-22 g Cu
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