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Formula’s

The Mole. Formula’s. Formulas. Empirical formula : the lowest whole number ratio of atoms in a compound. molecular formula = (empirical formula) n molecular formula = C 6 H 6 empirical formula = CH.

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Formula’s

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  1. The Mole Formula’s

  2. Formulas Empirical formula: the lowest whole number ratio of atoms in a compound. • molecular formula = (empirical formula)n • molecular formula = C6H6 • empirical formula = CH Molecular formula: the true number of atoms of each element in the formula of a compound.

  3. Formulas(continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl Al2(SO4)3 MgCl2 K2CO3

  4. Formulas(continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: C6H12O6 H2O C12H22O11 Empirical: H2O CH2O C12H22O11

  5. Empirical Formula • Empirical comes from Latin empiricus meaning a doctor relying on experience. An empirical formula must be obtained from experimental data. • The percent composition of a compound is the data you need to calculate the basic ratio of the elements contained in the compound. • The basic ratio, is called the empirical formula, gives the lowest whole-number ratio of the atoms of the elements in a compound.

  6. CH3 Empirical Formula • Smallest whole number ratio of atoms in a compound C2H6 reduce subscripts

  7. Empirical Formula…how to find it! 1. Find mass (or %) of each element. 2. Find moles of each element. 3. Divide moles by the smallest # to find subscripts. 4. When necessary, multiply subscripts by 2, 3, or 4 to get whole numbers’s.

  8. 1.85 mol 1.85 mol Empirical Formula • Find the empirical formula for a sample of 25.9% N and 74.1% O. 25.9 g 1 mol 14.01 g = 1.85 mol N = 1 N 74.1 g 1 mol 16.00 g = 4.63 mol O = 2.5 O

  9. N2O5 Empirical Formula N1O2.5 Need to make the subscripts whole numbers  multiply by 2

  10. C2H6 Molecular Formula • “True Formula” - the actual number of atoms in a compound CH3 empirical formula ? molecular formula

  11. Molecular Formula 1. Find the empirical formula. 2. Find the empirical formula mass. 3. Divide the molecular mass by the empirical mass. 4. Multiply each subscript by the answer from step 3.

  12. 28.1 g/mol 14.03 g/mol Molecular Formula • The empirical formula for ethylene is CH2. Find the molecular formula if the molecular mass is 28.1 g/mol? empirical mass = 14.03 g/mol = 2.00 (CH2)2  C2H4

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