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Chapter 19: Molecules and Compounds

Chapter 19: Molecules and Compounds. Section 19.3 Comparing Molecules. COMPARING DIFFERENT MOLECULES. How does the mass of different molecules compare?. Do you think that a molecule of water has the same mass as a molecule of calcium carbonate?. Recall atomic mass units (amu)….

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Chapter 19: Molecules and Compounds

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  1. Chapter 19: Molecules and Compounds Section 19.3 Comparing Molecules

  2. COMPARING DIFFERENT MOLECULES • How does the mass of different molecules compare?

  3. Do you think that a molecule of water has the same mass as a molecule of calcium carbonate?

  4. Recall atomic mass units (amu)… 6CCarbon12.0107 24 • Atoms are assigned a ________________ on carbon as the standard. • Known as atomic mass unit

  5. 19.3 Comparing Molecules

  6. Chemical formula gives 3 pieces of info: • _____ / _______ of atoms. • if ________ ions are present. • allows calculation of mass of 1 molecule of a compound relative to mass of other compounds.

  7. Formula Mass • Formula mass is determined by _____ up the atomic mass unit (amu) of all the atoms in the compound. • The atomic masses are listed on the ________ table.

  8. Example: Figuring Formula Mass • H2O means 2H and 1O • 2 (1.01 amu) =_____ +1 (16.00 amu) = ____ • Formula mass= ____ amu of H2O

  9. An amu is very small, so to be usable in measurements, we equate the _____________ of the formulamass in amu to an equalamount in _____.

  10. Avogadro’s Number • The formula mass in grams of any element or compound contains ____ ______ atoms or molecules. • Known as Avogadro’s # or a “____” of the substance.

  11. So, how do we use this value? • If you measure out 100.09 grams of CaCO3, you have 6.02 x 1023 molecules of CaCO3. • Likewise, 18.02 g of H2O contains 6.02 x 1023 molecules of water.

  12. Example: BaCl2 2H2O • 1 Ba = 1(137.30) = 137.30 • 2 Cl = 2(35.45) = 70.90 • 4 H = 4(1.01) = 4.04 • 2 O = 2(16.00) = 32.00 Formula mass = 244.24 amu

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