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Topic: Chemical Formulas Do Now: from last years regents

Topic: Chemical Formulas Do Now: from last years regents. Chemical Formulas. Tell type & number atoms in compound Microscopic level: Formula gives atom ratios Macroscopic level: Formula gives mole ratios. EXAMPLE. 2H 2 O can mean 2 molecules of water 4 H atoms & 2 O atoms

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Topic: Chemical Formulas Do Now: from last years regents

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  1. Topic: Chemical Formulas Do Now: from last years regents

  2. Chemical Formulas Tell type & number atoms in compound Microscopic level: Formula gives atom ratios Macroscopic level: Formula gives mole ratios

  3. EXAMPLE 2H2O can mean 2 molecules of water 4 H atoms & 2 O atoms 2 moles of water 4 moles of H atoms & 2 moles of O atoms NOTE: WATER IS A BINARY COMPOUND – contains 2 elements only

  4. What can say about CuSO45H2O? It’s hydrated salt – hydrate = water 1 mole CuSO4 contains 5 moles water 1 molecule of CuSO4 contains 5 molecules of water When heated, water is driven off & anhydrous salt is left: CuSO4 – anhydrous = without water mole ratio in formula can be used to predict how much water found in any size sample If had 2 moles of CuSO45H2O, how much water would you lose on heating?

  5. Hydrates • group salts that have water molecules stuffed in their empty spaces • Formulas are distinctive • Ex: CuSO45H2O  means “is associated with” or “included” • Does NOT refer to multiplication Not true chemical bond:

  6. CuSO45H2O • Count up the atoms! 1 Cu 1 S 4 O + 5x1 O = 9 O 5x2 H =10 H total = 21 atoms

  7. 5CuSO45H2O • Count up the atoms! 5 = Cu 5 = S 5x4 O + 5x5x1 O = 45 O 5x5x2 H = 50 H total = 105 atoms

  8. Types of formulas

  9. Empirical Formula Smallest whole # ratio of elements in compound CH4 C2H6 C5H10

  10. Molecular Formulas Gives exact composition of molecule CH4 C2H6 C5H10

  11. Ionic Compounds Metal and Nonmetal They are always empirical NaCl Fe2O3

  12. Molecular (Covalent) Compounds Nonmetal only Formulas can be empirical or molecular CH4 C2H6 C5H10

  13. Relationship between empirical and molecular formulas molecular formula is whole number multiple of empirical formula Molecular Formula = n (Empirical Formula) C4H8 = 4(CH2)

  14. Molecular Formula If know empirical formula and molar mass, can find molecular formula Example: Find molecular formula for substance whose empirical formula is CH and whose molar mass = 78.0 g Step 1: Find mass of empirical formula Step 2:Molar mass = whole # (n) Empirical mass Step 3: Multiply subscripts in empirical formula by n • Step 1: C = 1 x 12 = 12 • H = 1 x 1 = _1 • 13 g • Step 2: 78g = 6 13g • Step 3: 6 x subscripts in CH = C6H6

  15. Say everything you can about: NaCl C6H6 C6H12O6 CH4 CF4 BeSO4 C8H18 KI C2H4Cl2 CaBr2 CuSO45H2O Covalent, molecular Ionic, empirical Covalent, molecular Covalent, empir., molec? Covalent, empirical, molecular? Ionic, empirical Ionic, empirical Covalent, molecular Covalent, molecular Ionic, empirical Ionic, empirical

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