3.5 Empirical And Molecular Formulas

Question 1

What are empirical and molecular formulas?

Answer 1

The best was to identify an unknown compound is to determine its chemical formula

Question 2

Empirical formula

Answer 2

Lowest whole number ratio of elements in a compound

Question 3

Molecular formula

Answer 3

Indicates the exact number of atoms of each element in a compound

Question 4

What do some chemicals have in common and differ

Answer 4

• different chemicals can have the same empirical formula
• however, they will differ in structure and properties

Question 5

How do you get empirical formula from percent composition?

Answer 5

1. Percent to mass. Use 100 mg as a convenient mass if overall mass isn’t given
2. Convert to moles (use M)
3. Divide all by smallest number of moles
4. Multiply all by a number to get a whole value