Housekeeping: Your chemistry exam has been moved to November 25. You're simply not ready to take an exam in one week.
In regards to the empirical formula lab, there was simply no way to measure how much oxygen was used due to the fact that we did not have a proper seal on the evaporating dish, and because we had to open it to keep the magnesium ribbon lit, any gas used was lost. We also lost a fair amount of ash. I've done the math and there is no way to make it work without doing the lab again, and I'd rather not get caught up in that chicanery any time soon.
I've demonstrated how the calculations should look in your lab report, but you do need to address what went wrong in your Evaluation section. There is A LOT that went wrong, so your evaluation section will be quite lengthy.
As far as the LR/ER lab, I have completed the calculations that should be included in your lab report. We had some success with that experiment, so we can begin working on the lab report. We also need to determine the efficiency of the experiment using percent yield. Let's decide on a due date for the first draft in about two weeks. The final draft will be due two weeks after that.
Agenda:
1. Discussion of lab data and report writing.
2. Determining percent yield.
3. Introduction to Avogadro's Law & Gases
Lesson Objectives:
1. Explain the difference between actual yield and theoretical yield.
2. Complete percent yield calculations
3. Explain Avogadro's Law in relation to the behavior of gases.
Content Review:
Links: 1.3: Reacting Masses & Volumes
Textbook Readings: Section 1.3; p. 33-48
Student Missions:
Mission 1: Yield, Yield, YIELD!!! This six-minute vid explains the difference between theoretical, actual and percent yield.
In regards to the empirical formula lab, there was simply no way to measure how much oxygen was used due to the fact that we did not have a proper seal on the evaporating dish, and because we had to open it to keep the magnesium ribbon lit, any gas used was lost. We also lost a fair amount of ash. I've done the math and there is no way to make it work without doing the lab again, and I'd rather not get caught up in that chicanery any time soon.
I've demonstrated how the calculations should look in your lab report, but you do need to address what went wrong in your Evaluation section. There is A LOT that went wrong, so your evaluation section will be quite lengthy.
As far as the LR/ER lab, I have completed the calculations that should be included in your lab report. We had some success with that experiment, so we can begin working on the lab report. We also need to determine the efficiency of the experiment using percent yield. Let's decide on a due date for the first draft in about two weeks. The final draft will be due two weeks after that.
Agenda:
1. Discussion of lab data and report writing.
2. Determining percent yield.
3. Introduction to Avogadro's Law & Gases
Lesson Objectives:
1. Explain the difference between actual yield and theoretical yield.
2. Complete percent yield calculations
3. Explain Avogadro's Law in relation to the behavior of gases.
Content Review:
Links: 1.3: Reacting Masses & Volumes
Textbook Readings: Section 1.3; p. 33-48
Student Missions:
Mission 1: Yield, Yield, YIELD!!! This six-minute vid explains the difference between theoretical, actual and percent yield.
So how do we incorporate this into your LR/ER experiment? We will first determine the theoretical yield using the amounts we were given. This is something that will be included in your lab report, so you will be working with different data. Since we have our experimental (or actual) data, we have our actual yield. The percent yield is merely a ratio between these two numbers, with the AY as the numerator and the TY as the denominator. Multiply the result by 100 in order to obtain a percentage.
This describes the efficiency of the reaction. Percent yields that are at least 80% and up are considered decent. A PY greater than 90% is good. Anything lower and the experiment should be run again to increase its efficiency.
How efficient were your reactions? How would you increase efficiency? Think about what went wrong or the nature of your equipment.
Practice calculating percent yield.
Mission 2: That Dude's Back Again. You know, Avogadro. And this time, he's bringing flatulence into the mix. By flatulence I mean gas, and by gas I mean the behavior of gases in chemistry.
This describes the efficiency of the reaction. Percent yields that are at least 80% and up are considered decent. A PY greater than 90% is good. Anything lower and the experiment should be run again to increase its efficiency.
How efficient were your reactions? How would you increase efficiency? Think about what went wrong or the nature of your equipment.
Practice calculating percent yield.
Mission 2: That Dude's Back Again. You know, Avogadro. And this time, he's bringing flatulence into the mix. By flatulence I mean gas, and by gas I mean the behavior of gases in chemistry.
Avogadro's Law & The Nature of Gases. Recall that most of a gas' volume is empty space, so its chemical nature is irrelevant to its volume. The volume of a gas, therefore, is determined by the number of particles, temperature, and pressure. So if you have equal volumes of gases measured at the same temperature and pressure, it can be assumed that the equal volumes contain an equal number of particles. This is Avogadro's Law. Using Avogadro's Law as basis, the volume occupied by one mole of any gas (the molar volume) must be the same for all gases when measured under the same conditions of temperature and pressure.
To determine the number of moles in a gas, divide the given volume by the molar volume. It's similar to molar mass calculations.
At Standard Temperature & Pressure (STP), one mole of a gas has a volume of .0227 cubic meters/mole (22.7 decameters/mol). Standard temperature is 0 degrees Celsius (273 Kelvin) and standard pressure is 100 kpa (1 atm).
Let's practice playing with gas using this simulation.
Mission 3: Ideally, So To Speak...The ideal gas law is a hypothetical situation where gases behave according to the Kinetic Molecular Theory. Gas particles move in constant, straight-line motion and do not have intermolecular forces interacting on them, hence the term ideal. Of course, real gases do not behave ideally, but the IGL is a great starting point for understanding the nature and behavior of non-ideal gases.
To determine the number of moles in a gas, divide the given volume by the molar volume. It's similar to molar mass calculations.
At Standard Temperature & Pressure (STP), one mole of a gas has a volume of .0227 cubic meters/mole (22.7 decameters/mol). Standard temperature is 0 degrees Celsius (273 Kelvin) and standard pressure is 100 kpa (1 atm).
Let's practice playing with gas using this simulation.
Mission 3: Ideally, So To Speak...The ideal gas law is a hypothetical situation where gases behave according to the Kinetic Molecular Theory. Gas particles move in constant, straight-line motion and do not have intermolecular forces interacting on them, hence the term ideal. Of course, real gases do not behave ideally, but the IGL is a great starting point for understanding the nature and behavior of non-ideal gases.
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