Law of Definite Proportions Lab
1. Complete Pre-lab Questions
2. Generate Neat and Well Organized Data Table
3. Calculations (Include these answers in your Conclusion!)
a. Calculate the mass of magnesium that reacted by subtracting the mass of the crucible
and lid from the mass of the crucible, lid and magnesium.
b. Calculate the mass of magnesium oxide that was produced by subtracting the mass of
the crucible and lid from the mass of the crucible, lid and magnesium oxide.
c. Calculate the mass of oxygen that was reacted by subtracting the mass of magnesium
from the mass of magnesium oxide.
d. Find the mass ratio of magnesium to oxygen by dividing the mass of magnesium by the
mass of oxygen.
4. Questions
a. The accepted mass ratio of magnesium to oxygen in magnesium oxide is 1.52 g : 1.00 g.
How close was your final result to the accepted value? Why do you think this happened?
b. How would your results be affected if all the magnesium did not react?
c. Determine the correct formula for magnesium oxide. How does the mass ratio of
magnesium and oxygen compare to the ratio of elements in the chemical formula? Why
do you think this is?
5. Conclusion Paragraph
a. Restate the Purpose
b. Explain Calculations from Above
c. Describe two possible errors you may have committed in this lab that may have
somehow affected your results. Explain the specific steps you will take to avoid each of
these errors in the future.
Avoid use of personal pronouns