Percentage Composition

It is exactly what it sounds like. Percentage Composition.
This class we learned about Percentage Composition and it is quite simple.

Here is an example

What is the percentage composition of NaCl?

First of all you must calcuate the total Molar Mass(MM) of this compound

Total MM of NaCl: 23.0 + 35.5 = 58.5g/mol

MM of Na = 23.0 g/mol
MM of Cl  = 35.5 g/mol

From these numbers you calculate the percent composition of Na and Cl. (Round to 1 decimal place if the question does not give any numbers)

% of Na = 23.0g/mol
                 ------        x 100        =        39.3%                                % composition = mass of element
                 58.5g/mol                                                                                                  ---------------- x100
                                                                                                                                  mass of compunt
% of Cl  = 35.5g/mol
                 ------      x 100          =       60.7%
                 58.5g/mol

From these two numbers, the %  composition should add up to 100%.
Here is a video that explains another example of percent composition.



Here are the five questions and solutions we had to make.

1) What is the percent composition of Potassium carbonate? (K ₂ CO₃ )

Total MM of K2CO3 is :

K x 2 = 39.1 x 2 = 78.2 g/mol

C x  1 = 12.0 x 1 = 12.0 g/mol

O x 3 = 16.0 x 3 = 48.0g/mol

                          =  138.2g/mol
% of K = 78.2g/mol  /  138.2g/mol = 56.6%
% of C = 12.0g/mol  /  138.2g/mol = 8.7%
% of O = 48.0g/mol  /  138.2g/mol = 34.7%

2. Sodium Bicarbonate (sodium hydrogen carbonate) is basically baking soda. Its formula is NaHCO₃. Find the mass percentages (mass %) of Na, H, C, and O in sodium hydrogen carbonate.

Total MM = 84.0 g/mol

mass % Na = 23.0 g / 84.0 g x 100 = 27.4 %
mass % H = 1.0 g / 84.0 g x 100 = 1.2 %
mass % C = 12.0 g / 84.0 g x 100 = 14.3 %
mass % 3 * O = 48.0 g / 84.0 g x 100 = 57.1 %

3. Cetylpyridinium chloride, a common compound found in mouthwash, has a formula of C₂₁H₃₈NCl.
What is the percent composition?


21 C = 252 u
38 H = 38.0 u
1 N = 14.0 u
1 Cl = 35.5 u


Total MM = 339.5 g/mol


mass % 21 C = (252/339.5)100 = 74.2%
mass % 38 H = (38.0/339.5)100 = 11.2%
mass % 1 N = (14.0/339.5)100 = 4.12%
mass % 1 Cl = (35.5/339.5)100 = 10.5%

4. C₉H₁₁N₂O₄S is penicillin. Find the percentage composition for each Element.

Atomic mass

C9 = 108g/mol

H 11= 11g/mol

N2=28g/mol

O2 = 64g/mol

S = 32g/mol

Total MM = 234g/mol

% of C = 108/234 = 44%

% of H = 11/234 = 5%

% of N = 28/234 = 11%

% of O =64/234 = 27%

% of S = 32/234 = 13%

Did we get a sub and a quiz???? SIM

We got quite a long time to study for the quiz.  As soon as we walked in the cool teacher guy gave us time to study for our mole conversion quiz after we went over the homework.  After studying we had about 1 hr of class left so that means we had 1 hr to do our quiz.  About 20% finished quickly while the 80% including me finished near the bell.  When we handed in our work, we got THE WONDERFUL WORLD OF MOLES YUPPY and other work.  THE END to the super PRODUCTIVE day.  I learned a lot yay.

I learned a lot!

Harder Mole Conversions

HARDER?!?!? BUT HOW?!?!

Well, it is not so much harder as it is... more things to do.

We start, with a MOLE MAP

Made it myself. This is pretty much the entire lesson. If you find yourself nodding in satisfaction while reading it, you may stop here. If, however, you find yourself with either your left or right palm on your forehead, please proceed.

From the last post, you can learn how to apply these equations to convert your values. It is the basic conversion method. * Conversion factor refers to the value you must multiply by to obtain your initial number in converted units. It always has a division line with a numerator and denominator
1) Write your initial measurement
2) write the conversion factor so that the unit which you want to eliminate is on the opposite side. Ex if you wish to eliminate the mole unit, and it is in the numerator of your initial measurement, but the mole unit on the denominator of your conversion factor.
3) On the conversion factor, write the desired unit on the unfilled side of the division line.
4) On the conversion factor, put a 1 beside the larger of the two units. Beside the other unit, write the number of those units that go into the larger unit. Ex. 6.022 * 10^23 particles are in 1 mole, so put 6.022 * 10^23 beside the particles unit.
5) Cancel out the units that can be cancelled out, this leaves you with the desired unit
6) Multiply/Divide the numbers
7) Obtain new number in desired unit

However, new in this lesson, we have number of atoms in a particle.
To do this, count of number of X atoms in the formula and plug it in to where it says "# of atoms"
Ex. Convert 4.53 * 10^14 molecules of CO2 to amount of oxygen atoms
You count 2 atoms of O in CO2. Multiply 4.53*10^14 molecules by 2 atoms of oxygen/1 molecule.
4.53*2 = 9.06 ---> 9
9 * 10^14 atoms of oxygen

IT IS IMPORTANT TO KNOW THAT THERE IS NO SHORTCUT
In other words, there is no way to immediately jump from grams to particles. You must first convert to moles then to particles.

Ex. Find the mass of 3.67 * 10 ^11 molecules of phospate (PO4)
First convert to moles:
(3.67*10^11 molecules)(1 mole/6.022*10^23 molecules) = 6.0943208 *10^-13 moles
Now convert to grams:
(6.0943208 *10^-13 moles)(95 grams/1 mole) = 579*10^-13 ---> 5.79*10^-11 grams

Continue studying of the brown thing that goes underground

wow... okay I just deleted everything I did.... fail..

So I'll start over again~


YES MOLES!!! THOSE LOVELY LITTLE ANIMAL!!! WITH WEIRD FACE(the once with the star ....)

ALSO THIS MUST BE REMINDED IT IS AVOCADO'S NUMBER BECAUSE THE PERSON WHO FOUND THIS NUMBER IS SO IN LOVED WITH AVOCADO AND HE NAME IT AFTER IT

 Last class we studied converting moles to particles or grams
It was A REALLY FUNNNNN CLASS Since we learned something new~
yea since I deleted my intro before... I'll keep this one short

Okay so first convert particles to moles
If i have  5.0*10^12 particles of anything then how many moles would I have?
The equation for this is (number of particles) * (1mole/6.022*10^23particles)

5.0*10^12 particles	1mole
	6.022*10^23particles

So the answer would be 8.3*10^-12

Now let do it backwards from moles to particles
If I have 15 moles of carbon then how many particles would i have?

15moles	6.022*10^23particles
	1mole

So I would have 9.0*10^24 particles for 15 moles of carbon

Now let convert Mole into grams
Since what ever the atomic mass is is the molar mass so carbon with an atomic mass of 12 would have a molar mass of 12mol/g
So lets have an example question
If I have 91 moles of Uuq then how many grams would it be?

91moles	289grams
	mole

2.6*10^4 grams of Uuq if I had 91 moles of it

Okay now the other way around
If i have 5846 grams of Americium than how many moles would it be?

5846grams	mole
	243grams

So I would end up with 24.1moles of Americium~

http://www.fordhamprep.org/gcurran/sho/sho/convert/molecalc.htm this is an extremely good source if you didn't get the lesson

This is a little game that I found on the internet that is about moles the site is below
http://nobel.scas.bcit.ca/chemed2005/tradingPost/TUPM_S2_4_15ChemFunGames.pdf

The Great Mole Relay Race
Purpose: Students will work as a team in a relay race format in order to solve 1-step and
multi-step problems involving mass, moles, and representative particles.
Materials: Whiteboards mounted on wall, dry erase markers, slips of paper with different
problems printed on each
Set-up: You will want to separate your class into teams of about 3-6 people each. Be
strategic in your team formation so that no one team has a lop-sided advantage or
disadvantage. Each team will use a different section of the whiteboard.
Place the problems which are on the different slips of paper in cups labeled for each
team. Each cup will contain the same five or six problems, but students will choose the
slips at random, so that each team will probably be working on a different problem at any
particular time.
As teams work out the problems you will want to make sure you have a clear answer key
already written out so that you can check their work.
Game Play:
1) On your signal, the first student from each team will pick a slip of paper from his
team’s cup. He will then write the problem on the board in any form he chooses
so long as the rest of his team understands the problem (note: no one else is
allowed to look at the slip of paper). Player 1 then sits down.
2) Player 2 then heads to the board and begins the problem, proceeding through the
first conversion factor.
3) Player 3 then heads to the board and continues the problem by writing the next
necessary conversion factor.
4) Player 4 will write the next conversion factor, or if there is no need for another
conversion factor, she must use her calculator to correctly compute the answer
with units.
5) Check the answer. If it is correct, the next person may begin the next problem. If
it is wrong the next person must go to the board and figure out what is wrong and
fix it. This requires each person to be engaged in the whole problem. Require
each person to write each problem on his or her own paper. Collect all of their
work at the end of the game.
6) The winning team is the one that finishes all of the problems the fastest.

A little video that I found teaching the mole

The Mole

Say What? Ewww who would want to learn about those big brown things.

NO! This is chem class.

Okay this guy is Avogadro. This guy basically invented the mole.
One of the most important things to note is his hypothesis and it is named after him

Avogadro's Hypothesis
Equal volumes of different gases at the same temperature and pressure have the same number of particles

Enough with this charming looking dude.

You are still wondering what a mole is right? Right, because I have not told you yet.
The Mole allows chemistst to count atoms and molecules.

Avaogadro's Number

Yes children, the mole has a number. And this number is just 1 mole

Sorry but i cannot tell you how big it is. It is big. Very Big.

Back to Avogadro's hypothesis if there are the same number of particles in atom , the mass ratio is due to the mass of the particles. (used for the relative masses of all atoms on the periodic table.)

The mass of 1 atom of the element is counted in atomic mass units or amu.

Eg. Fluorine = 19.0 amu (because its atomic mass is 19)

When you want to find the mass of an ionic compound, you use the formula mass.

E.g. Potassium(K)+Fluoride(F)

         39.1            +   19.0 amu       =     58.1 amu

For covalent compounds, you use the Molecular mass.

E.g. Carbon Dioxide

          C        O2

           12 +   16.0x2

C02 = 44.0 amu

For pure substances, you use the atomic/molecular/formula mass in grams per mole)

Ex. 1 mole of oxygen is 16.0g/mol

Here is a song that we had in chem class talks about moles. Its fun.


But if you really want to learn about moles, watch this.

  

The TryHard Class

    Today we did quite a lot!  We worked VERY VERY VERY hard, we were given a review sheet on sci notation, sig figs and measuremants and uncertainty. Totally rad.  The purpose was to help us get ready for the test.  Btw  Joe had the worst accuracy and jennifer has the worst precision TROLOLOL.  Anyway we worked very hard on the review sheet VERY HARD LIKE GOOD STUDENTS and got most of the work done.  Occasionally we got a wtf r u doin and l2work look but otherwise it was all groovy.

 Cool story bro, nice review

After spending 4/6 of the class working on the review sheet, we started working on some real work.  Plotting graphs on excel.  We had to plot 3 graphs each on a different experiment.  One included volume of gas while other used density, etc.  We spent the whole time working very hard and plotting the graphs and answering questions on a hand out she gave us.  Turns out the worksheet was not even collected.  QQ i actually finished it.



This is basicly what we did but we chose scatter graph instead of column.

Last class, we did a lab as you may or may not have deduced from our previous post, which by the way, was the first lab blog not to include the words "super" and "fun" with the latter following the former. This was mainly due to the fact that we have banned Cole from making lab blogs.

ANYWAYS. We had a lab last class... BUT there was no lab report! WHAT A TWIST! Going all M. Knight Shyamalamadingdong on this blog, yo. INSTEAD, we had a lab quiz. BUT HOW?! How does one combine these two seemingly incompatible elements? By ingeniously transferring electrons from the metal element lab or La2+ to the gaseous element Quiz or Qu3-, the ionic compound Lab Quiz or La3Qu2! Actually, it was just a lab report disguised as a quiz, so I may have over hyped that a little.

The quiz consisted of hypothetical measurements and calculations with said measurements. Also, accuracy and precision was also discussed and a few hypothetical follow up questions that applied your knowledge of density and volume calculations. All of them must have incorporated scientific notation and significant digits, which was pretty much the underlying theme of the whole lab. It was more to test your sig-fig knowhow than to test your ability to make density calculations and weigh aluminum foil.

Apres le quiz, were taken to ze laBORaTORy of ze computers. There we made graphs from given data on a spreadsheet. The data was of the volume and mass of hot and cold water. Which this we found the density of both and the hot water was found to have slightly lower density than cold water. I concluded that this was because of the higher level of kinetic energy within the hot water, resulting in faster movement on more space between particles.

cool density experiment you can try AT HOME, except you probably don't have all this stuff

Another Fun and Excieting lab 2

Today we had a really fun day since we just had another LAB.~ But other than the lab we didn't really do much. So late me explain what happened during the lab. At first we were told what to do. Get 3 pieces of alumium foils and measure them. Then we are suppose to put each aluminum foil on the centigram and find out the mass of the the aluminum foil. After we found out the mass the volume of the foil were stated in the lab book and a simple calculation was able to show us the thickness. We repeated the calculations 3 to find out the 3 aluminum foils thickness. In the end we all had to calculate the percentage of error. (estimate - actual) / actual * 100, in absolute value. And for the rest of the class we basically didn't do anything yay~ free block~.

Density

So you're wondering, what is density and why is it important? Well since my vocbalulary is too intense, ill dumb it down a bit and sum it up in a few words. Density is a physical property of matter specified as mass per unit volume.  It is important because if you have two objects that have the same size, you can differentiate the two by calculating density from the following pyramid.

Mass = Density x Volume

Density = Mass / Volume

Volume = Mass / Density

Being a student the stress with memorzing formulas, please consider this pyramid because it can save your life. It also works in physics.

Some ways to represent density:

For a solid : g/cmᵌ

For a liquid: g/mL

1cmᵌ of water = 1mL

*If you want to know if an object floats or sinks, look at this equation below.

ᵈobjects > ᵈliquid = sink

ᵈobjects < ᵈliquid =float

Now for an example to help you with your problems.

Ex. Calculate the density of a solid gold house that has a mass of 133337g and a volume of 137.7L

Density = mass/volume                                                       D=133337g/137.7L

                                                                                          D=968.32g/L

Coke sinks, Diet coke floats. Aint that cool?