College Prep Chemistry
50 points
Core Lab #7
Determination of the Chemical Formula for Magnesium Oxide
Objectives:
1. To determine the simplest formula of magnesium oxide.
2. To prove the law of definite proportion through the synthesis of the compound magnesium oxide.
Introduction:
Hypothesis:
Chemical Reaction for the synthesis of magnesium oxide: ________________________________________________________
Procedure:
a. ***Safety reminder – you will utilize a Bunsen burner, glass labware, and handle hot objects – ensure that
long hair is tied back along with loose clothes and jewelry. You must also have closed toed shoes and safety
glasses on throughout the entirety of this laboratory procedure. ***
b. Complete the observations for Table 1 as the lab progresses.
c. Light the Bunsen burner and begin slowly heating a cleaned crucible. While one lab partner remains
with the lit Bunsen burner another should obtain a piece of magnesium as provided by the instructor.
d. Coil the magnesium as demonstrated by the instructor and obtain it’s mass.
e. After 3 minutes of moderate heating turn the Bunsen burner off and allow the crucible to cool. When
cooled enough (ask instructor if unsure) obtain the mass of the crucible.
f. Place the coiled magnesium ribbon into the bottom of the crucible and begin heating the crucible.
g. As demonstrated by the instructor – use the crucible top to seal the crucible after the magnesium
begins to ignite while simultaneously removing the Bunsen burner.
h. Mix the sample with a stir rod and then continue heating for another 3-4 minutes. After confirming with
your instructor that the reaction is complete, turn the Bunsen burner off and allow the sample to fully
cool.
i. Once fully cooled, slowly place 3- 6 drops of distilled water into the crucible. Carefully waft above the
crucible to detect any odors. Record observations.
j. Lastly, heat the sample very slowly to drive off any water. Allow it to fully cool and obtain the mass of
the crucible with its contents.
k. Thoroughly clean the crucible, clean up the lab bench, and double check that all gas valves are closed.
Data:
Table 1: Observations of Reactants and Products
Before Reaction
During Reaction
Table 2: __________________________________________
Mass of Crucible
Mass of magnesium ribbon (Mg)
Mass of crucible and contents after heating
Mass of crucible contents
Mass of oxygen combined with Mg
Analysis:
1.
2.
3.
4.
5.
6.
7.
Calculate the mass of magnesium oxide produced
Calculate the mass of oxygen reacted
Calculate the moles of magnesium reacted
Calculate the moles of oxygen reacted
Stem and leaf for moles of magnesium and moles of oxygen
Box plots for moles of magnesium and moles of oxygen
Summary of data table
Conclusion:
Sources of Error:
After Reaction
College Prep Chemistry
50 points
Core Lab #7
Determination of Chemical formula for Magnesium Oxide Rubric
Format
 Listed in table of contents (1)
 No personal pronouns (1)
 Lines skipped in written sections (1)
 Use appropriate units throughout and significant digits (2)
 Title all tables, graph, and figures (2)
 Tables and graphs are drawn with straight edge (1)
8 points
Introductory Paragraph
 Introductory statements
 Appropriate definitions
 Application of Chemistry explained
 Cohesive
5 points
Hypothesis
 Formula is determined
 Correct Lewis dot representation
2 point
Data /Analysis
 Chemical reaction (1)
 Table 1 &2 is completed appropriately (2)
 Calculations (3)
o Samples identified / work shown
o Correct answer
o Significant figures used
 Stem and Leaf (2)
o Scale
o Key
 Summary data table (2)
 Box plots (3)
o appropriate axis
o labels
13 points
Conclusion
9 points
 Restate the objective and incorporate how the objective was met by performing this lab (1)
 Address the objective. Support your answer with lab data and results (3)
 Defend your hypothesis using data from the lab. (2)
 Conclusion quality: well organized and cohesive and contains no mechanical/grammatical errors. (3)
o Well organized and cohesive but contains grammatical or mechanic(2)
o Somewhat organized but does not contain any errors (2)
o Somewhat organized with some errors (1)
o Disorganized with errors (0)
Sources of Error
______
 Identify 2 sources of error and the effect they would have on the experiment (3)
o Source of error
o Effect on data
3 points
o
Effect on result