Enthalpy Calculations

We begin with a story. Once upon a time there was a mole. One day, the mole disappeared. About 2 and a half months later, it returned. The end.

DELTA H ----> CHANGE IN ENERGY (kJ/mol)

But what does that mean? How do I find delta H?
CALM DOWN IM GETTING THERE.

Here's an example equation:

Ba + O2 --->  BaO + 1092kJ
Find delta H for 1 mole of product

STEP NUMERO UNO:
Look at it. Is it balanced? Is it equal? If I put both sides on either side of a scale would it even out? Yes, because they both weigh almost nothing? THAT IS BESIDE THE POINT. The point is, NO IT IS NOT BALANCED.

2Ba + O2 --->  2BaO + 1092kJ

Now, that looks much better.

STEP NUMERO DOS:

Take one part of the product side of the equation. In this case, only 2 BaO will do. Now take the energy (1092kJ) and put it into the form of kJ/mol like so:

-1092kJ/2 mol BaO

You may simplify this output to
-546kJ/1 mol BaO

So we just find delta H for these equations? NO
YOU CAN FIND ALL KINDS OF THINGS WHATEVER YOUR HEART DESIRES
except not, mostly just chemistry stuff

eg. Using the same equation (because im cool like that) Find the number of grams of O2 needed to produce 900 kJ of energy.

2Ba + O2 --->  2BaO + 1092kJ

Start with the energy needed to be produced:

-900 kJ

Find and utilize the conversion factor to end up with moles

(-900kJ)(1 mol O2/-1092) = 0.824 mol O2
Convert moles to grams:
(0.824 mol O2)(32g/1 mol O2) = 26.4 g

Asian guy explains everything

Endothermic and Exothermic Reactions

Sooo first of all, all chemical reactions involve changes in energy. Some release energy to the surroundings (exothermic) and others absorb it (endothermic)

Eg. Nuclear bombs give off energy and are exothermic reactions.

Eg. Ice starts to melt which absorbs energy and are endothermic reactions.

We use something called an Energy Diagram to chart the Potential energy of the chemicals as they change from reactants to products.

Before we get into the diagrams, here are a few vocabulary words you should consider remembering:

Energy of Reactants  -  total potential energy of all recatants in the reaction

Energy of Products  -  total potential energy of all products in the reaction

Energy of the Activated Complex  -  Potential energy of the "transition state" between reaction and products

Activiation Energy  -  the change in Enthalpy in Potential Energy during the reaction.

Change in Enthalpy  -  the energy that must be added to get the reaction to progress

If you still do not the concept of the Potential Energy Diagrams; watch this video.

SUPER LAB AWAAAAAYYYY!!!!

TODAY WAS A SUPER EPIC LAB NO JOKES. What did we do? Well go read lab 5b in your workbooks noobs. Lazy? Fine. Well anyway we did 7 experiments. These experiments were to look at different types of chemical reactions(ex. synthesis, single replacement, etc. Anway the first experiment required us to...


EXPERIMENT 1

take 6cm of copper and hold in on the hottest part of the flame for a few minutes. The copper turned pink surprisingly and it took a while to notice any change

EXPERIMENT 2

Place a nail into a test tube and add copper sulfate so that half the nail is covered. This was a unique experiment. In the begining it seemed as if nothign happend but soon half of the nailed (the part covered by the copper sulfate) turned pink. After 15 minutes we removed the nail and we were surprised to see that the WHOLE NAIL turned pink with splotches of red. Really cool.

EXPERIMENT 3

Pute solid copper sulfate PENTAhydrate into a test tube and heat it for a long time over a bunsen burner. Just like a previous experiment with a hydrate, this leaves over a coloured white sand with white flake remnant instead of a blue powder

EXPERIMENT 4

We add water to our result from experiment 3. The result, unexpectedly, turns back to normal after rehydrating it after it evaporated all its h2o.

EXPERIMENT 5

fill test tube 1/4 full with calcium chloride. Fill 2nd tube with sodium carbonate. Then mix them together. I thought something totally awesome would happen, and well it turned to a milky white solution....COOL.

EXPERIMENT 6

cover mossy zinc with hydrochloric acid. This is quite interesting actually. When added the solution continually keeps bubbling and rises. It keeps on doing this for over 20 minutes which surprised me. This reaction can go on for a looooooooong time.

EXPERIMENT 7

Half fill the tube with hydrogen peroxide and add a small amount of manganese oxide as a catalyst. THEN YOU HAVE TO QUICKLY light a match and stick it. IT ACTUALLY IGNITES! TRUE DMG AND OVER TIME OMFG. LIKE BAM. LIT. A SPARK FROM THE GAS, TOTALLY AWESOME....NO ONE WAS BURNED THOUGH....we tried to imitate this twice but .....no it was a one timer....

EXPERIMENT 8!!!!!!!!!!!!!!!!!!

THE MOST EPIC EXPERIMENT EVAR

MIX EVERYTHING TOGETHER AND SEE WHAT HAPPENS

BEFORE: EMPTY TUBE AND MANY MANY MANY THINGS

DURING: MIX EVERYTHING TOGETHER AND IT STARTS TURNING DARK GREEN

AFTER: IT TURNS BLACK BUT SOME SAID IT WAS DARK GREEN NOT BLACK O WELL

This is the hydrate experiment we did without the calculations he did

More Reaction Types

WHAT? MORE?!??! WHY OH WHY GOD HAVE YOU FORSAKEN ME!!?!?!

So yeah, looks like there are more of these to cover. None of which are new at all, so no need for the over dramatization.

Double Replacement

This is the Double Replacement reaction you know:
K2SO4 + BaCl2 ---> 2 KCl + BaSO4

Now here is that same reaction with the whole mess of crap that was added this year:

K2SO4(aq) + BaCl2(aq) ---> 2 KCl(aq) + BaSO4(s)

K(aq) + SO4(aq) + Ba(aq) + Cl(aq) ---> K(aq) + Cl(aq) + BaSO4(s)

Ba(aq) + SO4(aq)  ---> BaSO4(s)

As you may notice we have 3 separate equations. All of them however are essentially the same thing. The topmost is the balanced formula equation. (aq) determines that the item is aqueous while (s) determines that it is solid. To determine whether an item is aqueous or solid, use the table of solubility (all reactants are aqueous). The middle equation would be the Total Ionic Equation. To obtain this, separate all parts of the equation into individual elements or polyatomics, ignoring the coefficients. Items that are not aqueous cannot be separated. The last one is the net ionic equation which is obtained by cancelling items on either side of the total ionic equation like an algebraic equation.

Table of solubility

Combustion


This reaction consists of a chemical reacting with oxygen.

For hydrocarbons, the products will always include carbon dioxide and water
CH4(g) + 2 O2(g) ---> CO2(g) + 2 H2O(l)

For certain metals, the product will resemble a synthesis-like reaction
2 Fe(s) + O2(g) --> 2 FeO(g)

Neutralization


This reaction includes an acid + base as reactants and a salt + water as products. To form the salt take the chemicals that are not H or OH in the reactants and combine them in a synthesis like matter.

2 KOH(aq) + H2SO4(aq) ---> K2SO4(aq) + 2 H2O(l)


Thus conclude todays presentation. AND NOW FOR A VIDEO

Some nameless, faceless broad conducts a double replacement reaction in the name of SCIENCE. enjoy

Okay The MOST exciting lab we have EVER DONE

As the topic said This lab is SO FUN as most of us were astonished by the end of the class. The lab was sooooo fun. So you might be wondering what kind of lab did we do? IT IS A VIRTUAL LAB OMG. Instead of SEEING REAL RODS going BUBBLES we get to see some AWESOME Javascript animation that is totally easy to identify. Okay done with the random stuff. So what is this lab for? To learn more about single replacement and activity serious.

yea This is the real thing Cu(NO3)2

First we were presented 4 different kinds of solutions Mg(NO3)2, Zn(NO3)2,Cu(NO3)2, AgNO3 as we put the super cool animated rods into the solutions we got the results of Mg having the highest activity since it reacted with all of the solutions.

Then Cu rod was put in to the 4 solutions and only 1 rod changed there for it has less activity than Mg
After that Zn rod was inserted and 2 rod changed therefore Zn have higher activity than Cu but lower than Mg
and that leaves us with the last one Ag which didn't react with anything since it is the lowest of all in the Activity series. This is repeated with 4 other elements and it proves the activity serious.
Yep that is about all we did that class. and for the rest of the class most of us played around with the software and did our worksheet.
this is where we got our worksheet from in case you lost yours
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/Metal%3DMetalIonTutorialtgrt.pdf
and this is where the software is...
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/redox/home.html
yea this is just another exeriement done by someone else is about the same thing.


this is just cool. and it is single replacment double win