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Empirical and Molecular Formula Notes PowerPoint PPT Presentation

Empirical and Molecular Formula Notes. An Empirical Formula is a chemical formula for a compound that reflects the atoms contained in the compound in their smallest whole-number ratio. Examples: CH, BH, Ba (NO 3 ) 2 A Molecular Formula is the actual formula for a molecular compound.

Empirical and Molecular Formula Notes

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Empirical and Molecular Formula Notes

An Empirical Formula is a chemical formula for a compound that reflects the atoms contained in the compound in their smallest whole-number ratio.

• Examples: CH, BH, Ba(NO3)2

A Molecular Formula is the actual formula for a molecular compound.

• Examples: C2H2, B12H12, Ba3(NO3)6

• An empirical formula may not be a correct molecular formula.

• Steps to Solve Empirical and Molecular Formula Problems

Determining the correct Empirical Formula

• Look at the formula subscripts. Are they in their smallest whole-number ratio?

• If yes, then you are done.

• If no, then divide each subscript by their largest common denominator.

• Example: C2H6F4 has en empirical formula of CH3F2since all of the original subscripts were divisible by 2.

• Steps to Solve Empirical and Molecular Formula Problems…continued

Determining the correct Molecular Formula

• Determine the molar mass of the empirical formula.

• Divide the molar mass of the sample by the molar mass of the empirical formula.

• Multiply the subscripts of the empirical formula by the answer.

• Example: the empirical formula of the sample is CH and the sample molar mass is 104.16 g/mol.

• CH has a molar mass of 13.03 g/mol

• (104.16 g/mol ) / (13.02 g/mol)= 8

• The Molecular Formula is C8H8

I

Empirical and Molecular Formula Practice

Determine the empirical formula.

1. C6H6 C3H3

Determine the molecular formula.

2. A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. What is the molecular formula of this compound? C4O2H8

We

Empirical and Molecular Formula Practice …continued

Determine the empirical formula.

3. C6H18C4H9

Determine the molecular formula.

4. A compound with an empirical formula of C4H4O and a molar mass of 408 grams per mole. What is the molecular formula of this compound? C8H8O2

You

Empirical and Molecular Formula Practice …continued

Determine the empirical formula.

5. C14H42O14CH3O C4H9

Determine the molecular formula.

6. A compound with an empirical formula of CFBrO and a molar mass of 636.75 grams per mole. What is the molecular formula of this compound? C2F2Br2O2