Hess's Law Lab

Friday was a pretty simple day in Chemistry. We started off class by going over the procedures for Hess's Law Lab. Here are some tips that might help you with the lab: When you are trying to find the heat of reaction for Reactions 1 and 2 you have to use q=mc∆t. Once you find J, all you have to do is divide that by 1000 to put it into kJ and then divide the kJ by the moles of magnesium/ magnesium oxide used in the experiment. Once you find the heat of reaction for both experiments, use Hess's Law to find the heat of reaction for the combustion of magnesium.

And the next Scribe is Rachel K.

We are making silver!!!

Today we started off class by going over question #3 on the SuperMole Fun worksheet. The point of this problem is to find the amount of bacteria tissue (C5H7O2N) produced. In the problem you are given the kg of waste to start (10000 kg). You need to convert this into NH4+ ions so you multiply by 3.o kg NH4+ / 100 kg waste. Since the problem says the waste water contains 3% NH4+ ions, we can assume 100 kg. After converting to NH4+, multiply by 1000g / 1 kg so the equation is converted to grams. Next, you find the molar mass of NH4+, which is 18.04. Multiply the equation by 1 mol NH4+ / 18.04 g NH4+ to convert it into moles. After this you use the conversion factor 1 mol C5H7O2N / 55 mol NH4+ to convert the equation into moles of C5H7O2N. Next, you find the molar mass of the bacterial tissue which is 113 g and use the conversion factor of 113 g / 1 mol C5H7O2N to convert the equation into grams. The grams of bacterial tissue produced should be 34000 g. Once you have found this, multiply it by 0.95 (95%) because in the problem it says that only 95% of ammonium (NH4+) ions are consumed by the bacteria. If you had some trouble following this, the answers and work are posted here. After going over the worksheet, we started our Copper and Silver Nitrate Lab by going over the pre lab and procedures. This lab is going to take multiple days, so we haven't finished it yet, but it is due on tuesday of next week. Also, our class could probably make a huge profit by saving all our silver from the lab, just throwing that out there.

Everyone better watch the Bears own the Dolphins tonight. And the next scribe is...

Faith S.

Percent Error

Today was a pretty relaxed day in 7th period chemistry. We started out class by turning in our Penny Density Lab. After that, Mr. Lieberman went over question 6 in the post lab, which was finding the percent error in our experiment. The equation to find the percent error is:

You are probably going to need to know this equation so memorize it! Also, Mr. Lieberman stressed the point that even if our data is wrong, as long as our data supports our answer, it is okay. After going over the Penny Lab, we started on Part A of the Beverage Density Lab. In this lab, we were looking for the percent sugar content in several different beverages. We started off this lab by going

over Pre-Lab question 3 on how to calculate the sugar content. To find the

sugar content percent, you first have to multiply the given volume (355 mL) by

the given density (1.043 g/mL) which comes out to be 370 g. Next, you divide

the sugar mass (49 g) by the total mass (370 g) to get the percent sugar content in the beverage. After explaining the Pre-Lab,Mr. Lieberman took us through

the procedure of our Lab and then we got started. Also, in the lab, we changed the volume of 10.00 mL to 5.00 mL when measuring the substances. That

basically sums up what we did today in class, and now here is an awesome

density song.

The homework for tonight is to create a graph for our lab tomorrow and our

test is on Thursday.

The next Scribe is... Joe R.