1. Determining the Molecular Weight of a Substance from its Formula

2. Why is Molecular Weight Important? The molecular weight of a substance is the weight in atomic mass units of all the atoms in a given formula. (Remember that one atomic mass unit is roughly equal to one proton or neutron.) Knowing the molecular weight will help you to be able to identify what specifically is going to happen or what is happening in a chemical reaction. Molecular weight is something you can measure with a balance.

3. Visit the site below: http://dbhs.wvusd.k12.ca.us/Mole/Mo lecWt.html

4. Question #1—(answer in online lab notebook) How many atoms does the molecule K 2 SO 4 contain?

5. Question #2 How many different elements does the molecule K 2 SO 4 contain?

6. Question #3 How many potassium (K) atoms does K 2 SO 4 contain? How many sulfur (S)? How many oxygen (O)?

7. Question #4 What is the molecular weight of K 2 SO 4 ?

8. Question #5 How many oxygen (O) atoms does Al(MnO 4 ) 3 contain?

9. Question #6 What is the molecular weight of Al(MnO 4 ) 3 ?