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Using Chemical Formulas

Using Chemical Formulas. I can determine the formula mass and Molar mass for any compound. Formula Mass. The formula mass of any molecule, formula unit, or ion is the sum of the average atomic masses of all the atoms represented in is formula. Formula Masses/Molar mass.

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Using Chemical Formulas

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  1. Using Chemical Formulas I can determine the formula mass and Molar mass for any compound.

  2. Formula Mass • The formula mass of any molecule, formula unit, or ion is the sum of the average atomic masses of all the atoms represented in is formula.

  3. Formula Masses/Molar mass • Find the sum of all the atoms, this unit will be in amu (average atomic mass) • To due this you must first determine the amu’s for the individual atoms and then add them together. • Remember you find the amu of an atom based on the atomic mass on the periodic table • Subscripts equal the number of atoms or moles

  4. Formula Mass Example • Example: H2O • 2 H atoms x 1.01 amu/1 H atom = 2.02 amu • 1 O atom x 16.00 amu/ 1 O atom = 16.00 amu • 2.02 amu + 16.00 amu = 18.02 • 18.02 is the average atomic mass or the formula mass of water

  5. Practice • Find the formula mass of Magnesium Chloride?

  6. Practice • Find the molar mass of barium hydroxide?

  7. Molar Mass as a Conversion Factor • The molar mass of a compound can be used as a conversion factor to relate an amount in moles to a mass in grams for a given substance. • Amount in moles X molar mass (g/mol) = mass in grams

  8. What is the mass in gram of 2.50 mol of oxygen gas? • Given: 2.50 mol O2 • Unknown: mass of O2 in grams • Formula : mol X molar mass (g/mol) = mass • Step one find the molar mass of O2 • 2 mol O X 16g O/ mol O = 32g O2 • Step two solve for mass of O2 • 2.5 mol O X 32 g O2 / mol O2 = 80 g O2

  9. Practice • What is the mass in grams of 2 mol of AlF3?

  10. Molar mass • Convert from grams to moles and molecules. • 6.60 g (NH4)2so4 HOW MANY MOLES? How many atoms?

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