units for entropy

I misspoke in class the other day. The correct units for entropy are (j/mole K). That means that you have to put your entropic values in Kilojoules in order to use them in the gibbs free energy formula!!! Plz pass this on

Entropy

***NOTE*** this is Bobby Shaw's post, he just didn't have access to our blog so I'm posting it for him.

We started off class today with lab review I am going to type on of the reactions that we reviewed and if you have any questions about the second two reactions, post a comment and I, or someone else, will do their best to answer.

REACTION ONE
Mg + 2HCl ------> MgCl2 + H2
You can use q=mc
BUT WAIT HOW DO YOU GET THE MASS!!!!
Though only the people who got the Mg would know you use a simple conversion factor of
After that you would find the moles of magnesium by these equation

REMEMBER – this was done twice – you need to do the process above two times and then calculate the average. THIS GOES FOR ALL THREE REACTIONS DON’T FORGET THIS THE MORE ACCURATE YOU ARE THE LOWER YOUR PERCENT ERROR WILL BE

Once you have all three of the equations done you need to use Hess’s law AND SHOW YOUR WORK. This work should be shown in the evidence section that lap


CHEM NOTES

Seeing As the slide share link always takes me to gun manuals I am going to type out my notes.

1. We started with spontaneous reactions
2. A SPONTANEOUS REACTION IS A REACTION THAT TAKES PLACE ON ITS OWN WITHOUT OUTSIDE FORCES
a. there are a few things to be worried about though, LIKE
i. It does not have to start on its own so long as it carries out the rest of the experiment
ii. If it spontaneous in one direction then it is not spontaneous in the other direction
3. Examples of spontaneous reactions
a. Hydrogen ballon reaction
b. Paint can explosion
c. Ice cube melting
d. RUBBER BAND
i. This was the one we spent the most time on
1. The reason that it is such a good example was because when a rubber band is left to sit, it is going to sit there and not move. No matter how much you want something to happen without touching the rubber band, it wont happen. However if stretched out and then contracted, that contraction is a spontaneous reaction because it goes from being stretched out to a normal state with no outside influence
ii. You should not that spontaneous reactions have nothing to do with speed.
iii.
e. Nature allows spontaneous reactions
i. Nature divides spontaneous reactions in two main ways
1. Maximum probability – this is where everything mixes
2. Minimum probability – nature has the chance to become disordered but does not
4. ENTROPY
a. Entropy is denoted with “S”
b. Defined as – the increase in disorder or randomness
i. Nature always wants to move toward a positive entropy
c. MICROSTATES: different ways molecules can be distributed
i. Increase of microstates = an increase of entropy
ii. large number of microstates = large probability of different states = higher entropy
d. FACTORS THAT INFLUENCE ENTROPY
i. Liquid has a great entropy than solid
ii. Gas has the highest
e. CALCULATING ENTROPY
i. Very similar to calculating enthalpy
1. It is
2. REMEMBER COEFFICIENTS ARE USED IN THE EXACT SAME WAY WHEN CALCULATING ENTROPY AS THEY ARE WHEN YOU ARE CALCULATING ENTHALPY
a. If there are 2mol of something you multiple by 2 etc

d


This video does a good job summarizing the lesson today.

Alright well I am about done there are just a few announcements you should be aware of

1. Today is Kathryn J’s birthday if you haven’t wished her a happy birthday DO IT
2. Mr. Lieberman has his ear pierced, though he never wears it
3. The lab is due tomorrow
4. There is a web assign due Wednesday
5. The class would like to congratulate Mollie and Emilio for… Well, being Mollie and Emilio ;)
6. We got a Worksheet today that you should do
7. Everything for this chapter including both sets of book problems will be due on Thursday and if we have a snow day on Wednesday well then I am not sure.
That’s about it for today. The next scribe is Ben T, enjoy

Hess's Law Lab

Hey everone! Friday was another interesting day in Chemistry. After everyone got seated, Mr. Lieberman talked to us about the days activity, which included a Hess's Law Lab. After going over the procedure, we got in our lab groups, put on our visorgogs, and got to work.

First, we made our date tables, which should ideally include two separate areas (for Equation A and Reaction #2) with spaces for two trials. We began Equation A by measureing two strips of magnesium ribbon and recording that in our data table. We then massed a clean dry calorimeter, and remassed it once we added 15 mL of HCl (recording both in the data table, of course). We took the initial temperature of the HCl, and then added a piece of magnesium to the calorimeter. We stirred the piece as it dissolved, and then retook the temperature once it was constant. Once that was over and we recorded all of those temperatures and masses in our data table, we repeated!

Then, it was on to Reaction #2. We remassed the calorimeter (once it was clean and dry), and remassed once we added 15 mL of HCl. To switch things up, we then added about .20 g of magnesium oxide. We recorded the masses of the calorimeter, as well as the actual mass of the magnesium oxide in our data table. Once we added the magnesium oxide in the calorimeter, we stirred until the temperature remained constant. We recorded this temperature and then repeated the whole process!

Once this lab was over, we left chemistry to go enjoy our weekends. Don't forget to work on this lab, though, it's due Tuesday! Good luck to Bobby S, our next scribe, on his first post for Period 6!

Hess's Law

Through our excitement filled class today, we not only got a glimpse at carbon dioxide and nitrogen's triple point, but we also learned about the amazing science that is Hess's Law. We started off with a demo, where we were instructed to put on our trusty viser-gogs and crouch around the front table. Assuming the lab was going to be a harmless one, as the dry ice started to melt, we slowly got closer. With Mr. Lieberman encouraging us to get a closer look, we were all surprised when it exploded, showering everyone with water. This caused more then a few screams, one of which from the notorious Korri and even the stoic people of the class were startled by this outburst.

From there we moved on to Hess's Law, as depicted in slides 33-59 in the following slides:

Hess Law And Thermodynamics

View more presentations from dluetgens.

After learning about this law and Mr.Lieberman's super power affiliated with it, we observed Nitrogen's triple point. This we used a vacuum to ensure an extremely low pressure and though it was not as thrilling as the last, the outcome was interesting to watch. The bubbles rose and dropped continuously as the pressure reached the triple point. From then to the end of the class we proceeded to practice more enthalpy problems which we all somewhat mastered by the end.

Make sure to do the homework and practice practice practice as it makes perfect.
And the moment you've all been diligently checking the blog for is here! The next scribe will be...Ellen H. congratulations

All About Phases

Today in chemistry class we started out by learning about phase diagrams. They are representations of the state of substances based on the temperature and pressure conditions. The pressure is listed on the y-axis( in mmHg) and the temperature on the x-axis (in degrees celsius). The points on the graph indicate that states are in equilibrium. Point A, the triple point, is a point where all three states are in equilibrium. If a substance is gotten to exactly the right temperature and pressure of its triple point, all three states will be present.

We learned that the state of a substance can be manipulated by using pressure. For example, a tank of propane gas used for grilling is kept at high pressure in order for it to remain in liquid state in the tank before it is needed. However, when the valve is open to get the propane gas to the grill, the pressure is lessened and the propane needed is changed to gas form.

Mr. Lieberman did a demo where he simulated boiling by putting dry ice in a beaker of water. He said that once the pressure in the gas bubbles equals the pressure in the water, vapor will be formed.

Mr. Lieberman also did a demo that proved that pressure affects the state of water and any other pure substance. He put a beaker of water inside a vacuum and started lowering the pressure. The water started boiling within 30 seconds and produced vapor.

Lastly, Mr. Lieberman showed us dry ice in all three states by putting some in a tube and sealing all the holes. He then held this tube into a beaker of water and we watched the dry ice turn into liquid form from its solid state. Also, we saw vapor bubbles frequently during many attempts at perfecting this demo. These vapor bubbles indicated the presence of a hole in the seal of the tube. Finally we saw dry ice in liquid form!

This has been Korri H!!

The next scribe is Katie I.

Don't forget to do the worksheet!