Monday, December 13, 2010

To start off class today, Mr. H handed us a lab procedure sheet for the Molar Volume Lab. He then told us the purpose of the lab which is to determine the volume of one mole of gas at STP. After Mr. H briefly explained the lab, we got into our groups and started the experiment.

My groups data looked like this:
Barometric Pressure: 763.52 mm Hg
Length of Mg strip: 3.8 cm
Mass of Mg strip: 0.05 g
Density of Mg strip: 0.00995/3.8= 0.0026 g/cm
Temperature of water: 20.1 degrees Celsius or 293.1 Kelvin
Volume of gas: 61.5 mL

After each group finished up the data part of the lab, Mr. H showed us Brooke's blog from Friday which had some really important information about the five equations used for solving gas related problems.

We then started off the lesson on page 15 with Gas Stoichiometry Calculations. Mr. H taught us that Avogadro's Law is used in these types of problems which are very similar to conversions we did in previous chapters. Avogadro's law states that one mole of any gas occupies the same volume when held at the same temperature and pressure.

The first problem that involved finding the volume of a certain compound was #4.
Our first step in solving this problem is to write a balanced equation:
C3H8(g) + 5O2(g) ------> 3 CO2(g) + 4 H2O(g)
Then the question told us to determine the volume of CO2 that is produced at STP.
In order to solve this question, you have to make a conversion factor problem:
149 g C3H8 * 1 mol C3H8 * 3 mol CO2 * 22.4 L CO2/44 gC3H8.
The reason I used the number 22.4 L is because if a gas is at STP then there are 22.4 L of that certain gas.
The final answer would be approximately 228 L CO2.

After we did this, we did one more problem on page 16, #6 and the answer was 44.8 L H2.
Then we went back to our lab to record the data measurements and after this class was over.

HW: WebAssign due tomorrow, Test on Friday, Unit 6 Delicious due Thursday, WebAssign due Wednesday, and 3 WebAssigns due on Friday.