no more tears

Elizabeth Kurburski
Mr. Ochs
Honors Chemistry
March 8, 2013

How Do Chemical Reactions Affect the Percent Yield of Magnesium Oxide?
Abstract: The lab was done heating a crucible and magnesium to create a chemical reaction that burns the magnesium to find the percent yield. First, the crucible and lid was washed, heated slowly using a Bunsen burner to ensure that it didn’t crack, and then both massed. Next, magnesium oxide was put into the crucible and massed again. Then the magnesium oxide was burnt. When the magnesium oxide ignited, the lid was put on to keep in the escaping mass of the smoke. When the magnesium oxide turned orange the reaction was done and cooled and massed again. The ending mass is supposed to be as close to 100% yeild as possible.
Introduction: The purpose of this lab was to gain the highest level of percent yield from the reaction of the magnesium oxide, to hopefully keep 100% of the magnesium oxide. Percent yield is found when the actual is divided from the theoretical mass of what we should have got. The Law of Conservation of Matter states that no more than 100% can be gained because matter cannot be created or destroyed, it can only escape. The matter is still there when smoke escapes, but it isn’t destroyed. The goals of this report are to have the least amount as possible lost in the reaction. Matter is lost when the lid is off for too long letting the smoke escape, after the magnesium oxide has reacted. The hypothesis for this lab was to get around, or as close to, a 74% yield. The reasoning of this was the group anticipated errors to happen and our history of reports going well is low. Also, it is very easy to let matter escape in the smoke with the lid being off after the reaction.
Materials and Methods:
See attached page
Results – Qualitative:
The overall findings of the lab were that mass was lost after the reaction. The mass didn’t stay the same as when started, so a small amount of the mass of magnesium oxide was lost.  This is because smoke escapes the crucible when the lid is open, causing a decrease in the mass. Matter can only escape and not be created or destroyed, so the findings were correct with the Law of Conservation of Matter.

Results-Quantitative:
Another observation graph on page 2.
Phase	Mass of Crucible, Lid, and MgO
Before	37.201
After 	35.026

Legend – This graph shows the mass crucible, lid and magnesium oxide on a digital scale. The graph shows that after the reaction mass was lost.
Discussion I:
	See Page 3
Discussion II: The hypothesis was 74% and was a decreasing percent yield compared to the 94.15% that was obtained during this experiment. It was assumed that it would be very difficult to get close to the 100% yield, because of the possible ways to let the matter escape. Matter had escaped due to the smoke being released because the lid wasn’t on the crucible fast enough. According to the Law of Conservation of Matter the mass of magnesium oxide could not be created nor destroyed. The reason why the percent yield was 94.15% was due to the fact that the matter had escaped, but not destroyed. First, for the lab the crucible was heated very slowly to ensure that the crucible wouldn’t crack, because that could possibly change the mass and let the magnesium oxide smoke escape. The lid had to be put on very quickly so that the smoke couldn’t leave. The biggest issue with the lab was due to the crack that formed during the end of the lab, which could have been avoided if the crucible was heated slowly.

Conclusion: In this lab the Law of Conservation of Matter was proven, through finding the percent yield of a compound after a reaction occurs. The Law of Conservation of Matter states that matter cannot be created nor destroyed. The results show that matter was destroyed, but it was in fact, just smoke escaping when the lid was opened. The lesson learned from this lab is that the Law of Conservation of Matter was correct.  The group also learned how to capture the smoke that was released from a reaction and how to mass the magnesium oxide on a digital scale very precisely. The scale was very precise and the slightest movement could change the mass. With a percent yield of 94% the lab was a resounding success. The hypothesis wasn’t exactly as the results were, but the outcome was very close to the 100% yield success.
Citations: Law of Conservation of Matter found in Modern Chemistry Book

vWhat will the percent of magnesium oxide be after a reaction takes place?
Abstract: to do the lab you must first heat a crucible and magnesium to create a chemical reaction that burns the magnesium to find the percent yield. First, the crucible and lid was washed, heated slowly using a Bunsen burner to ensure that it didn’t crack, and then both massed. Then, magnesium oxide was put into the crucible and massed again. Then the magnesium oxide flamed and burnt itself out. When the magnesium oxide started fire, the lid was put on to keep in the escaping smoke. When the magnesium oxide turned orange the reaction was done and cooled and massed again. The ending mass is supposed to be as close to 100% yield as possible