A student who was in a hurry to complete this experiment did not follow the exac
ID: 506847 • Letter: A
Question
A student who was in a hurry to complete this experiment did not follow the exact directions for some of the procedural steps. Briefly explain what effect, if any, the following changes would have on the whole number ratio of Mg and O in the compound the student produced. (1) When arriving at the laboratory station, the student found a dirty crucible and cover. In the interest of time, the student skipped Steps 2-8, weighed the crucible and cover, and proceeded directly to Step 9. (2) While heating the Mg m the crucible, the cover fell onto the laboratory bench and broke. The student found a new cover and used it for the remainder of the experiment. (3) After adding water to convert any Mg_3N_2 to magnesium oxide, the student completely covered the crucible while doing the final heating. (4) Because the crucible seemed to be taking forever to cool, the student decided to make the final weighing when the crucible was still slightly warm.Explanation / Answer
1. If the crucible is not washed and dried properly, the dirt in the crucible will increase the weight of the crucible. After the experiment the weight of the crucible may not be same if some dirt adhered to the outside of the crucible falls of or removed while handling it during the experiment. If that happens total mass of the oxide calculated after the experiment will come to be larger than what it actually is. Thus the ratio of Mg and O will appear to be smaller than reality.
Also, if the crucible contained some other compounds initially which reacts with the gas inside the crucible on heating, then total mass of the oxide calculated after the experiment will appear to be bigger than what is is actually and the ratio of Mg and O will appear to be smaller than reality.
2. If the new lid is heavier than the original one then total mass of the oxide calculated after the experiment will appear to be bigger than what it is actually and the ratio of Mg and O will appear to be smaller than reality.
If the new lid is lighter than the original one then total mass of the oxide calculated after the experiment will appear to be smaller than what is actually and the ratio of Mg and O will appear to be larger than reality.
3. When water is added to convert Mg3N2, NH3 vapor and water vapor produces in the crucible. If the crucible is completely covered then the ammonia and water vapor will remain in the crucible and total mass of the oxide after the experiment will appear to be larger than reality. So the ratio of Mg and O will appear to be smaller than what it actually is.
4. If the crucible is warm, the metal part of the balance may expand which will ultimately contribute to an error. Moreover warm interior of the crucible can create an air current inside and around the crucible which will give an unsteady and incorrect result.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.