CHEM 2115 Lab Report
Experiment #4
Name
Magnesium Oxide
Section #
1. Data
Station #
Trial 1
Chem I Lab
Date
.
Trial 2
Mass of crucible & lid
Mass of crucible, lid, & Mg
sample
Mass of Mg sample
Moles of Mg
Mass of crucible, lid, and
magnesium oxide
Mass of magnesium oxide
Mass of oxygen that combined
with Mg
Moles of monatomic oxygen
Mole ratio: Mg/O
Experimental mass% Mg
Experimental mass% O
Average Values
Mole ratio of Mg/O
Experimental % Mg
Experimental % O
Experimentally determined empirical
formula of magnesium oxide
Attach sample calculations of each type necessary to obtain the results in the above table. These should
include the equations used, substituted values, and results.
2. If a 0.192 g sample of copper metal reacts with elemental sulfur to form 0.240 g of the sulfide product, (a) find
the percent by mass of copper and sulfur in the product and (b) find the empirical formula of the copper sulfide.
Please show your work.
3. Data Analysis: Class data for this experiment is available on Blackboard. Use Excel to determine
the values for the mass % magnesium and mass % oxygen for each data set in your class and find the
class averages. Prepare a Table of Results in Excel that has 2 columns and 5 rows. Label the columns
for the mass % of magnesium and oxygen. Label the rows for (1) your average value, (2) the class
average, (3) the theoretical value, (4) your difference, relative to the class value and (5) the class
relative error. Definitions of relative difference and relative error are given on page IV-3 of the Lab
Manual. Include a printout of this table along with your lab report form.
Mass % of
Magnesium
Your Average Value
The Class Average
The Theoretical Value
Your Difference, Relative
To The Class Value
The Class Relative Error
Mass % of
Oxygen
A. Discuss how well your results for the weight % magnesium agree with the class results. (Since the
magnesium and oxygen results are related, only the magnesium results need be discussed.) In this
discussion, refer to the data in your Table of Results. You may wish to write this portion of your
report on the computer and paste the Table of Results from Excel directly into it. You should note
which student data points, if any, were excluded. The goal of this discussion is to compare your
experimental work to the class average.
B. Discuss how well the class results agree with the theoretical expectation by referring to the class
relative error from the Table of Results.
C. Conclude your discussion by reporting the mole ratio of magnesium to oxygen, calculated from the
class values for the experimental mass % magnesium and oxygen. Using this value, report the empirical
formula of magnesium oxide and compare it to the theoretical formula.
4.
A. Suppose that the magnesium is not polished at the start of the experiment.
Would the
experimentally determined percent magnesium be too high, too low, or unaffected by this procedure?
Explain why.
B. In a hurry to complete the experiment a student spilled their crucible and lost some of the magnesium
oxide product before the final weighing. Will the experimentally determined percent oxygen be
reported too high or too low? Explain you answer.