some lab thing..........you work with another pair......yay

ummm yea.....we had a lab....sooo fun.. 6D to be precise.  This experiment is unique in that it takes 2 days to do it.  The purpose of this is to determine which reactant is limiting and which is excess.

ok we wore our super cool stuff.  Then we obtained 2 reactants known as Na2Co3 and Cacl2.  We weighed them both and then  we combined them in a 25ml beaker and waited for 5 minutes.  We probably waited for 13 min and 42 sec but whos counting?  Anyway we then set up a ringstand with a paper funnel in the hole of the ringstand( must be folded triangularly bro and weighed).  underneath the filter paper was a clean beaker.  We then poured our 13 min and 42 sec combined solution into the filter paper and waited....and waited...for like 18min and 21 sec.  Then we found out we had a murky white substance in the beaker and some left over residue in the paper funnel.  We then saved our filter paper to weigh next time.  From our experiment we can conclude we had an excess and limiting reactant!!

yea i had to do this

 Na2CO3 + CaCl2 ---> CaCO3 + 2NaCl
this is the reaction and when we weigh the precipitate left behind in the filter paper we can determine which reactant is excess and which is limiting and by how much! omg so exciting






This is how you fold the filter paper

Limiting and Excess Reactants

OK party people let MC JayLiu drop these beats on excess and limiting reactants

NO, that was NOT lame. In fact it's what all the fly kids by saying these days. Word

OKAY. So we see two terms from the title alone. Excess and limiting reactants? Let me put it in a way that most people can relate to.

Let's say for some unknown reason you want to make me a sandwich. Ingredients and supply? BREAD 10 pieces. SALAMI 489 slices. My sandwich consists of two pieces of bread with 267 slices of salami in between, no more, no less.

When we take a look at our bread supply, we see that we have to make five sandwiches. GREAT! Let's make 5 sandwiches.

HALT, EVIL DOER!

LOOK AGAIN, and you will see that we have a mere 489 slices of salami, enough to make 1 sandwich.

Therefore: only 1 sandwich can be made due to a LIMITING supply of salami, even though we have EXCESS bread. Also, JayLiu's 4th law of stoichiometry: One can never have EXCESS salami.

like this, without all that green crap

NOW, let's move away from the art of sandwich craft and move to ACTUAL Stoichiometry.

Eg. Butane burns in the presence of oxygen to form carbon dioxide and water. If 12.0g of butane reacted with 46.0g of oxygen, which reactant is excess/limiting and how many grams of CO2 will be produced?

STEP 1: WRITE THE EQUATION AND BALANCE

2 C4H10 + 13 O2 ------> 8 CO2 + 10 H2O

STEP 2: CONVERT ONE MASS INTO THE OTHER

(12.0g C4H10)(1 mol C4H10/58g C4H10)(13 mol O2/2 mol C4H10)(32g O2/1 mol O2) = 43.0g O2

since 43.0g < 46.0g, C4H10 is the limiting reactant by 3g

STEP 3: USING LIMITING REACTANT, FIND PRODUCT

(12.0g C4H10)(1 mol C4H10/58g C4H10)(4 mol CO2/1 mol C4H10)(44g CO2/1 mol CO2) = 36.4g CO2

Not the first video that appears when searching the query: "limiting and excess reactants".... the second

Molarity and Stoichiometry

This is an add-on from the previous blog.
This add-on costs $19.99
If you purchase this add-on you will be one step closer in reaching your Stoichiometriness.

BUY NOW

Aight, since you bought this add-on you will learn about Molarity.

Lets start with some examples

Eg. How many grams of Calcium will be formed when 100mL of 0.500M CuSO4 is reacted with sufficient Ca?

FIRST Make the equation
1 CuSO4 + 1 Ca ----> 1 CaSO4 + 1 Cu
Second Check if it is balanced
Now convert mL to L and convert to moles
0.100 L x 0.500Mol CuSO4
                ---------------- = 0.05 moles CuSO4
                         1 L
Now convert moles of CuSO4 to moles of Ca

0.05 mol CuSO4 x 1 mol Ca
                              ----------             =   0.05 moles
                              1 mol CuSO4
Now convert moles of Ca to grams by multiplying by the molar mass of Ca

0.05 mol Ca x 40.1g Ca
                       ---------    =   2.005 grams (REMEMBER SIG FIGS) =  2 grams
                       1 mol Ca

Here is a video to help you



Another part of your add-onn is
GAS STOICHIOMETRY (STP)

Here is an example of a gas stoichiometry problem

Zinc Carbonate decomposes into CO2 and Zinc Oxide. How many grams of ZnCo3 are needed to produce 8.0L of CO2 measured at STP?

First make your equation and balance it
1 ZnCO3 ---> 1 CO2 + 1 ZnO

Then convert litres into moles of CO2 to moles of ZnCO3

8.0L x 1 mol C02           1 mol ZnCo3    
           -----------      x   -------------- =   0.35714 moles ZnCO3
           22.4L CO2          1 mol Co2
NOW convert moles of ZnCo3 to grams

0.35714 mol ZnCo3 x  125.4 g ZnCO3
                                    ----------------  =  44.785356g ZnCO3 Round to sig figs 45g ZnCO3
                                      1 mol ZnCO

If you are still having some problems, please visit this website for more info
http://www.chemtutor.com/xmol2.htm

AN ADD ON TO THE SUPER FUN W/E HE WROTE....its down below

You see, the last blogger wrote some random stuff about molar ratio and finding moles of different elements....yay....thats such loser stuff. THIS IS THE REAL STUFF.  This is what seperates pros from well people like the last blogger.  Anyway this is an add on to his lesson, this goes further into what stoichiometry is all about....annoying the heck out of people.

Instead of just finding moles of this and that, this time we will convert something like 5 moles of oxygen to 10 grams of what the hell.  The first step is to write out a balanced equation and find the molar ratios.  Then you will convert the number of moles of one element to another element.  Then you would do the same conversions you did in the previous chapters such as multiplying by 6.022 to the power of 23 to find the number of atoms.

It seems confusing and yes it is but this example will explain everything!  If not go read another blog or read the last bloggers post and then read another blog.

                                                  1 PbCl2 + 1 Mg = 1 MgCl2 + 1 Pb

find out how many grams of lead is needed to react with 5 moles of Mg.  Using the mole ratio we look at the place we are going over the where we are.  So when we convert it, it turns to 5 moles Pb.  Now we turn Pb into grams.  We multiply it by its molar mass.  It should be 207.2 times 5 =  1036 grams. The answer is we need 1036  grams of lead is needed to react with 5 moles of Mg.

Now if we changed the question to how many atomes of Pb is needed to react with 48.6 grams of Mg.  Then we will have to change Mg to moles by dividing it by its molar mass and it will be 2.  Then doing the exact same use the molar ratio from Mg to Pb and you will get 2 moles of Pb.  Now instead of going to grams you are going to molecules.  You are going to multiply 2 moles of Pb by 6.022 to the power of 23.  Now that is your answer.

Some cool teacher person talking for a long time non stop about some chemistry thing.  Not sure what it has to do with anything but watch it anyway. She literally talks for the whole time, go grab some popcorn its gonna be a long day.




cool story teacher, very cool.  Gonna watch that again

OMG ANOTHER FUN AND EXCITING CLASS!!!!

Today we learned about the proness of  MOLE + WORD EQUTIONS OMG OMG OMG OMG. How hax is it? I have no idea but we all know because it is chemistry it have to be FUN! Right? Yep that’s my into for today and maybe next time when I am more creative I’ll write more or other stuff but today isn’t my creative day. OKAY ON TOPIC So what did we learn today? We learned about this thing called st-----metry yea something like that... After looking through an immense amount of books many scholars finally decided on Stoichiometry. So what does Stoichiometry mean??? Honestly I have no idea, but according to Wikipedia it is about the quantitative analysis of chemicals reactions and measuring the amount of elements and compounds involved in a reaction. So basically it means measuring chemicals in numbers and the number of elements and compound in an reaction. What does Stoichiomety help us find out? It find how many molecules of whatever element that is in a reaction that the reaction started with. So is this thing useful? Not really but its life so we have to learn it. Going back  a bit Stoichiometry can be separated into 2 Greek words stoichio which menas elements and metry is measurement.

Let’s start with an example

I have 90000 Cl and 1 Na what will I get?

9000Cl+1Na à NaCl + 8999Cl

Even though I have over 9 thousand of Cl I can only produce 1 NaCl because Na is the limiting factor.

First Q

C3H8+5O2à 4H2O +3CO2 how many grams of H2O will be produced if I burned 215G of C3H8?

First make everything into moles

215g C3H8 * mol C3H8/44GC3H8 = 4.89 mol C3H8

4.89 molC3H8 * 4mol H2O/1mol C3H8 = 19.5mol H2O

19.5mol H2O* 18gH2O/1mol H2O = 352g H2O

There done

More questions

the number of moles of carbon dioxide formed when 40.0 mol of oxygen is consumed in the burning of propane.

C₃H₈ + 5O₂ à 3CO₂ + 4H₂O

Molar Ratio 3 CO₂ / 5 O₂

40.0 mol O₂ x 3 mol CO₂ = 24.0 mol CO₂

                          5 mol O₂

A piece of iron (10moles) was dissolved in HCl. The reaction formed H₂ and FeCl₂ amount of FeCl2 formed and amound of HCl used.

  Fe + 2HCl = FeCl₂+H₂

10 mol Fe * 1mol FeCl2/1mol Fe  = 10mol FeCl2

HCl = 2(Fe) --> 20 moles of HCl was used.

Super typical chem teacher teaching on youtube.