Interconverting masses - so, 1.5 moles of CaCl2 would be:...

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Interconverting masses, moles, and numbers of particles Keeping track of units in calculations is necessary when interconverting masses and moles. This is formally known as dimensional analysis . "Igor! bring me 1.5 moles of calcium chloride" Chemical formula of calcium chloride = CaCl 2 Molecular mass of Ca = 40.078 amu Molecular mass of Cl = 35.453 amu Therefore, the formula weight of CaCl 2 = (40.078) + 2(35.453) = 110.984 amu (remember, this compound is ionic, so there is no "molecular" weight). Therefore, one mole of CaCl 2 would have a mass of 110.984 grams.
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Unformatted text preview: so, 1.5 moles of CaCl2 would be: (1.5 mole )(110.984 grams/mole ) = 166.476 grams "Igor! I have 2.8 grams of gold, how many atoms do I have?" Molecular formula of gold is: Au Molecular weight of Au = 196.9665 amu Therefore, 1 mole of gold weighs 196.9665 grams. So, in 2.8 grams of gold we would have: (2.8 gram )(1 mole/196.9665 gram ) = 0.0142 mole From Avogadro's number, we know that there are approximately 6.02 x 10 23 atoms/mole. Therefore, in 0.0142 moles we would have: (0.0142 mole )(6.02 x 10 23 atoms/mole ) = 8.56 x 10 21 atoms...
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