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EMPIRICAL FORMULA

EMPIRICAL FORMULA. ANSWERS. 1. Determine the empirical formula of a compound that contains 2.94 g oxygen and 1.96 g sulfur. 2.94 g oxygen x --------------- = 1.96 g sulfur x ----------------- =. 1 mol. 0.184 mol. 16 g. 1 mol. 0.0613 mol.

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EMPIRICAL FORMULA

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  1. EMPIRICAL FORMULA ANSWERS

  2. 1. Determine the empirical formula of a compound that contains 2.94 g oxygen and 1.96 g sulfur. • 2.94 g oxygen x --------------- = • 1.96 g sulfur x ----------------- = 1 mol 0.184 mol 16 g 1 mol 0.0613 mol 32 g THIS COLOR - USE THE PERIODIC TABLE

  3. 0.0613 S = --------- = 1 0.0613 • Divide each by the smallest amount of mol. SO3 0.184 O = -------- = 3 0.0613

  4. 2. What is the empirical formula of a compound that contains 40.3% potassium, 26.8% chromium, and 32.9% oxygen? • 40.3 g K x --------------- = • 26.8 g Cr x ----------------- = • 32.9 g O x ---------------- = 1 mol 1.03 mol 39 g THIS COLOR - USE THE PERIODIC TABLE 1 mol 0.525 mol 52 g 1 mol 2.06 mol 16 g

  5. 1.03 K = --------- = 2 0.525 • Divide each by the smallest amount of mol. 2.06 O = -------- = 4 0.525 0.525 Cr = -------- = 1 0.525 K2CrO4

  6. 3. A compound is 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen. Find the empirical formula. • 65.5 g C x --------------- = • 5.5 g H x ----------------- = • 29.0 g O x ---------------- = 1 mol 5.46 mol 12 g THIS COLOR - USE THE PERIODIC TABLE 1 mol 5.5 mol 1 g 1 mol 1.8 mol 16 g

  7. 5.45 C = --------- = 3 1.8 • Divide each by the smallest amount of mol. 1.8 O = -------- = 1 1.8 5.5 H = -------- = 3 1.8 C3H3O

  8. 4. What’s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65% oxygen? • 18.7 g Li x --------------- = • 16.3 g C x ----------------- = • 65 g O x ---------------- = 1 mol 2.67 mol 7 g THIS COLOR - USE THE PERIODIC TABLE 1 mol 1.36 mol 12 g 1 mol 4.06 mol 16 g

  9. 2.67 Li = --------- = 2 1.36 • Divide each by the smallest amount of mol. 4.06 O = -------- = 3 1.36 1.36 C = -------- = 1 1.36 Li2CO3

  10. MOLECULAR FORMULA ANSWERS

  11. 1) A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. • C = 12 g x 2 = 24 g • O = 16 g = 16 g • H = 1 g x 4 = 4 g • +____ • 44 g Molar mass --------------- Empirical Formula mass 88 g ------ = 2 44 g C4H2O8

  12. 2) A compound with an empirical formula of C4H4O and a molar mass of 136 grams per mole. • C = 12 g x 4 = 48 g • H = 1 g x 4 = 4 g • O = 16 g = 16 g • +____ • 68 g Molar mass --------------- Empirical Formula mass 136 g ------ = 2 68 g C8H8O2

  13. 3) A compound with an empirical formula of CFBrO and a molar mass of 254.7 grams per mole. • C = 12 g = 12 g • F = 19 g = 19 g • Br = 80 g = 80 g • O = 16 g = 16 g • +____ • 127 g Molar mass --------------- Empirical Formula mass 254.7 g -------- = 2 127 g C2F2Br2O2

  14. 4) A compound with an empirical formula of C2H8N and a molar mass of 46 grams per mole. • C = 12 g x 2 = 24 g • H = 1 g x 8 = 8 g • N = 14 g = 14 g • +____ • 46 g Molar mass --------------- Empirical Formula mass 46 g ------ = 1 46 g C2H8N

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