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February 24, 2014

February 24, 2014. Chemical Formulas The Mole One-Step Molar Conversions. Materials. Calculator Periodic Table A good attitude about math. Chemical Formulas. Covalent: C 8 H 18 Octane # Carbon: 8 # Hydrogen: 18 Ionic: Al 2 (SO 4 ) 3 Aluminum Sulfate # Aluminum: 2 # Sulfur: 3

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February 24, 2014

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  1. February 24, 2014 • Chemical Formulas • The Mole • One-Step Molar Conversions

  2. Materials • Calculator • Periodic Table • A good attitude about math

  3. Chemical Formulas • Covalent: C8H18 • Octane • # Carbon: 8 • # Hydrogen: 18 • Ionic: Al2(SO4)3 • Aluminum Sulfate • # Aluminum: 2 • # Sulfur: 3 • # Oxygen: 12 • (4 O’s in each sulfate, 3 sulfates in the compound, 3 x 4 = 12)

  4. Formula Mass • The mass of one molecule, formula unit, or ion. • Calculate by adding atomic masses together from the periodic table. • Units: amu (atomic mass unit)

  5. Example: HCl • Mass H + Mass Cl • 1.0079 + 35.453 = 36.4069 amu

  6. Example: NH4NO3 • Mass N + 4(Mass H) + Mass N + 3(Mass O) • 14.007 + 4(1.0079) + 14.007 + 3(15.999) = • 80.0426 amu • OR • 2(Mass N) + 4(Mass H) + 3(Mass O) • 2(14.007) + 4(1.0079) + 3(15.999) = • 80.0426 amu

  7. Example: PO43- • Mass P + 4(Mass O) • 30.974 + 4(15.999) = 94.97 amu • The charge does not affect the mass because the mass of an electron is so very small that it is negligible (able to be ignored).

  8. And now: MOLES

  9. The Mole • 1 mole = 6.02 × 1023 particles • It is the number of atoms in exactly 12.0 g of carbon-12 • It is used the same way as: • A dozen (12) • A pair (2) • A score (20) Avogadro’s number

  10. How did they come up with 6.02 x 1023anyway? • If you divide the charge on a mole of electrons by the charge on a single electron you obtain a value of Avogadro’s number of 6.02214154 x 1023 particles per mole.

  11. Chemical Formulas • Covalent: C8H18 • Octane • Moles Octane: 1 • Moles Carbon: 8 • Moles Hydrogen: 18 • Ionic: Al2(SO4)3 • Aluminum Sulfate • Moles aluminum sulfate: 1 • Moles Aluminum: 2 • Moles Sulfur: 3 • Moles Oxygen: 12

  12. Molar Mass • Mass of one mole(6.022 × 1023) of any molecule, formula unit, or ion. • Calculate by adding atomic masses together from the periodic table. • Units: g/mol

  13. Example: H2SO4 • 2(Mass H) + Mass S + 4(Mass O) • 2(1.0079) + 32.066 + 4(15.999) • 98.0178 g/mol

  14. Example: Ca(NO3)2 • Mass Ca + 2(Mass N) + 6(Mass O) • 40.078 + 2(14.007) + 6(15.999) = • 164.086 g/mol • OR • Mass Ca + 2((Mass N) + 3(Mass O)) • 40.078 + 2((14.007) + 3(15.999)) = • 164.086 g/mol

  15. Molar Conversions Amount in moles Mass in grams • Divide by the molar mass • Multiply by the molar mass

  16. Example: How many moles are in 2.0 g calcium chloride? • Start with: g • End with: moles • Math: divide by molar mass • Molar mass of calcium chloride, CaCl2 • 40.078 + 2(35.453) = 110.984 g/mol • 2.0 g CaCl2= 0.018 mol 110.984 g/mol

  17. Example: How many grams are in 1.5 molpotassium iodide? • Start with: moles • End with: g • Math: multiply by molar mass • Molar mass of potassium iodide, KI • 39.098 + 126.90 = 165.998 g/mol • 1.5 mol x 165.998 g/mol = 248.997 g

  18. Molar Conversions • Number of particles • Formula unit • Molecule • Ion • Atom Amount in moles Multiply by Avogadro’s # Divide by Avogadro’s #

  19. Example: How many formula units are in 6.0 molcalcium bromide? • Start with: mol • End with: formula units (particles) • Math: multiply by Avogadro’s number • 6.0 mol x 6.02 x 1023 =3.612 x 1024 f. units • Calculator Help: Use the EE button • EE = x 10 • 6.02 x 1023 = 6.02EE23

  20. Example: How many moles are in 5.0 × 1022 molecules H2? • Start with: molecules (particles) • End with: moles • Math: divide by Avogadro’s number • 5.0 x 1022 molecules= 0.083 mol • 6.02 x 1023 molecules/mol • Calculator Help: Use the EE button • 6.02 x 1023 = 6.02EE23

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