Download 5.06 Lab Report

Percent Yield Lab Report
Instructions: For this investigative phenomenon, you will need to determine the percent yield of
magnesium oxide from the given reaction to determine if it is a useful commercial process.
Record your data and calculations in the lab report below. You will submit your completed
report.
Title: Percent Yield Lab
Objective(s): Find the percent yield of Magnesium Oxide for commercial processes
Hypothesis:
No hypothesis needed for this lab. Your theoretical yield calculation serves as your prediction for
what you expect the lab to produce, and that will be determined later in the lab.
Procedure:
Access the virtual lab. Because this lab is virtual, summarize the steps used to collect your data.
In addition, list and explain your controlled variables, independent variable, and dependent
variable for this lab.
Materials:
Percent Yield Virtual Lab
Variables:
Remember, controlled variables are factors that remain the same throughout the
experiment. An independent (test) variable changes so that the experimenter can see the
effect on other variables. The dependent (outcome) variable will change in response to
the test variable.
Controlled variables: Mass of the empty crucible, scale, and time on bunsen
burner
Independent Variable: Mass of magnesium
Dependent Variable: Mass of crucible with contents
Summary of Steps:
Data:
Type the data in the data table below. Don’t forget to record measurements with the correct
number of significant figures. Hint: Using the same instrument, you should have the same
number of digits to the right of the decimal.
Data
Mass of empty crucible with lid
Mass of Mg metal, crucible, and
lid
Mass of MgO, crucible, and lid
Trial 1
Trial 2
26.698 (g)
27.060 (g)
26.687 g
27.046 g
27.291 g
27.273 g
Calculations:
Show your calculations for each of the following. Remember, calculations should
follow rules for significant figures.
1. Write the balanced chemical equation for the reaction you are performing.
2Mg(s) + O2(g) = 2MgO(s)
2. Subtract the mass of the crucible and lid (row 1 in the chart) from the total mass
of Mg, crucible, and lid (row 2 in the chart) to find the mass of magnesium for
each trial.
 Trial 1: .253
 Trial 2: .325
3. Subtract the mass of the crucible and lid (row 1 in the chart) from the total mass
of MgO, crucible, and lid (row 3 in the chart) to find the mass of magnesium
oxide for each trial. This is the actual yield of magnesium oxide for each trial.
 Trial 1: .415
 Trial 2: .512
4. Magnesium is the limiting reactant in this experiment. Calculate the theoretical
yield of MgO for each trial.
 Trial 1: .251
 Trial 2: .310
5. Determine the percent yield of MgO for your experiment for each trial.
 Trial 1: 98.9%
 Trial 2: 98.2&
6. Determine the average percent yield of MgO for the two trials.
98.8%
Conclusion:
Write a conclusion statement that addresses the following questions:


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Explain why the product had a higher mass than the reactant, and how this relates to
conservation of matter.
What sources of error may have contributed to the percent yield not being 100 percent?
(Think about things that may have led to inaccurate measurements or where mass of the
product could have been lost if this experiment was conducted in a physical laboratory.)
How do you think the investigation can be explored further?
One reason on why the products has a higher mass then the reactant is because of the burning
of magnesium. When magnesium burned, it lost some mass, so it got smaller in size. Percent
yield can not go higher than hundred percent, it depends on how the magnesium burned could
affect it. This experiment can be explored further by using other elements rather than
magnesium or maybe using a different state of matter, or even freezing it. Basically, the product
had a higher mass than the reactant because of the law of conservation of matter. This law
states that matter can never be created or destroyed, but only trade places, or be transferred.
The reactants were just ‘transferred” into another product.
Post-Lab Reflection Questions
Answer the reflection questions using what you have learned from the lesson and your
experimental data. It will be helpful to refer to your chemistry journal notes. Answer questions in
complete sentences.
1. When conducting this experiment, some procedures call for heating the substance several
times and recording the mass after each heating, continuing until the mass values are
constant. Explain the purpose of this process and how it might reduce errors.
There is a greater chance of having more accurate and precise data outcomes when one takes the
time and records the data. This again would also help to increase the percent yield since they will
know the strong and weak points.
2. Your company currently uses a process with a similar cost of materials that has an
average percent yield of 91 percent. If the average percent yield of this process is higher
than that, this could save the company money. What is your recommendation to the
company? Please support your recommendation using your data, calculations, and
understanding of stoichiometry gathered from this lab.
I would do a lot of different experiments to try my best to make the percent yield higher
since that would let the company have a better outcome rate to display to the public. Ninety
one percent is a pretty high percent yield but getting to one hundred is very hard, but one
can still try by raising the percent yield through experiment. My recommendation to the
company is to try doing varying experiments with different measurement, temperatures,
and the time.