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TOPIC 3

TOPIC 3. The Mathematics of Formulas & Equations. GRAM FORMULA MASS. Recall The mass of 1 proton is 1 amu The mass of 1 neutron is 1 amu The mass of an electron is negligible. GRAM FORMULA MASS. Recall

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TOPIC 3

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  1. TOPIC 3 The Mathematics of Formulas & Equations

  2. GRAM FORMULA MASS • Recall • The mass of 1 proton is 1 amu • The mass of 1 neutron is 1 amu • The mass of an electron is negligible

  3. GRAM FORMULA MASS • Recall • The atomic mass of an element is found in the top left corner of each element box on the Periodic Table

  4. GRAM FORMULA MASS • Recall • The number of atoms of each element present in a compound is denoted by the subscripts on each element

  5. GRAM FORMULA MASS • Gram formula mass is the mass of the smallest unit of a compound from the sum of the atomic masses of all atoms present

  6. GRAM FORMULA MASS • GFM of K2CO3 • K – (39.1 g)(2 atoms) = 78.2 g • C – (12 g)(1 atom) = 12 g • O – (16 g)(3 atoms) = 48 g_ 138.2 g GFM of K2CO3 is 138.2 g

  7. PERCENT COMPOSITION • Percent Composition represents the composition as a percentage of each element compared with the total mass of the compound

  8. PERCENT COMPOSITION • % composition = x 100 (on RT) mass of part mass of whole

  9. PERCENT COMPOSITION • Find the % of K, Cl & O in KClO3 • Find the GFM (mass of whole) K – (39.1 g)(1 atom) = 39.1 g Cl – (35.5 g)(1 atom) = 35.5 g O – (16 g)(3 atoms) = 48 g__ 122.6 g

  10. PERCENT COMPOSITION • Plug the mass of each element (mass of part) and the GFM into the % composition equation % K = 39.1 / 122.6 = 32 % % Cl = 35.5 / 122.6 = 29 % % O = 48 / 122.6 = 39 %

  11. MOLES • 1 Dozen bagels = 12 bagels • 1.5 Dozen bagels = 18 bagels • 1 mole of KClO3 = 122.6 g of KClO3 • 1.5 moles of KClO3 = 183.9 g of KClO3 • 1 mole = 6.02 x 1023 particles • 1 mole = 22.4 L

  12. MOLES • Number of moles = given mass / GFM (on RT) How many moles is equivalent to 4.75 g of NaOH? Na – (23 g)(1 atom) = 23 g O - (16 g)(1 atom) = 16 g H - (1 g)(1 atom) = 1 g GFM = 40 g # of moles = 4.75 / 40 = .119 moles of NaOH

  13. MOLES • Number of moles = given mass / GFM (on RT) How many grams is in 2.8 moles of NaOH? Na – (23 g)(1 atom) = 23 g O - (16 g)(1 atom) = 16 g H - (1 g)(1 atom) = 1 g GFM = 40 g 2.8 = given mass / 40 → 112 g of NaOH

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