Lab 5B: sometimes it's CHEMISTRY

Hola to our fellow blog readers! As all of you already know, today is a lab day for us, and we're going to further explore the topic of chemical reactions in this blog (*cough cough* pull yourselves together girls, we're NOT going to make love potions or anything related to that) Instead, we'll be discussing about 7 different chemical reactions. They're not exactly as exciting as the methane-rocket we did the other day, but they're way better than the aluminum foil.

Now, may I ask all of you to put on your safety goggles and lab coats, we're about to start our experiments!

Reaction 1:Burning Copper

For our first experiment, we're going to burn a piece of copper wire under a flame. First, turn on the Bunsen burner and adjust the flame to high heat (blue color), then hold the wire over the flame, with a pair or tongs, of course! (Do not try to hold it with your hands...or you'll have an extra dish for your lunch....)

Now, observe as the copper is burning. The blue flame has turned into green color, while the wire has turned to brown-ish-black. This is a simple synthesis reaction between copper and oxygen in the air. The chemical equation can be written as the following:

4Cu + 1O₂ → 2Cu₂O

Reaction 2: Rusting Iron Nail

Time to move on to our next experiment! Now we're going to rust a piece of iron nail. First, we need to clean the nail with a piece of steel wool and make sure its surface is shiny. Then, prepare some copper(II) sulfate in a test tube which half covers the nail we put in. Copper sulfate is a blue colored salt that is mostly used as a fungicide, which is, to kill fungi, spores, and mushrooms. The chemical reaction is a single replacement, where the iron has combined with sulfate, forming sheets of coating.

1Fe + 1CuSO4 → 1FeSO4 + 1Cu

Reaction 3 and 4: Dehydrating a hydrate

Our third experiment will be removing water from copper(II) sulfate pentahydrate by burning this solid over a flame. (Hmm..."dehydrating a hydrate"...don't you like the oxymoron?) As you recall what we did before in Lab4C, a hydrate is a compound that contains water molecules. When it is heated, it'll give off water, leaving the anhydrous salt behind. 

During heating, the hydrate will turn green gradually, and then completely white. If we add several drops of water to the anhydrous salt, it'll turn back to it's originally state as a blue-colored hydrate.

This is a decomposition reaction.

1CuSO4‧5H2O → 1CuSO4 + 5H2O

Reaction 5: Forming Precipitate

Calcium chloride is a salt which is widely used as brine to prevent roads from freezing, treating hypocalcaemia patients, or even flavoring pickles. Sodium carbonate, on the other hand, is mostly used in manufacturing glass. These solutions both have a clear color when dissolved in water, so be careful and do not mistaken them as water, they are not good for your health. Now back to our experiment, mixing these solutions together and you'll get a precipitate forming, it is a double replacement reaction.

1CaCl2 + 1Na2CO3 → 1CaCO3 + 2NaCl

Reaction 6: Dissolving Zinc

Now, moving on to our next task. This time, we'll use hydrochloric acid to cover a piece of mossy zinc in a test tube. As the acid is dissolving the metal, we'll see  lots of bubbling, and it also gives off heat! This is an example of a single replacement reaction.

1Zn + 2 HCl  →  1ZnCl2 + 1H2 + Heat

Reaction 7: The Ultimate Classic

Here's our LAST experiment for the day; and the last one is always the best. 

We're going to pour hydrogen peroxide solution into a test tube, and then add a bunch pinch of manganese(IV) oxide into the solution. In this case, manganese oxide acts as a catalyst to help decomposing hydrogen peroxide into water and oxygen. In order to test this theory, we put a burning glowing splint into the test tube while it's releasing O2 gas. The splint will then grow into a larger flame when it is in contact with oxygen gas.

2 H2O2 → 1O2 + 2 H2O

So this pretty wraps up our lab for today, you guys can put clean up all your equipments now, and don't forget to wash your hands before going. Also, remember to study for the fiesta (aka: quiz) on Monday! Mr(or Mrs)PinchOfKCN will always be proud of you!

Oh, and one LAST thing before we end this lesson, here's a combustion reaction between methanol and oxygen experiment performed under safety guidelines, so do not try to do this experiment at home :)

And here's something unrelated to chemistry but interesting enough to caught your final attention: calculating the acceleration and velocity of this methanol-rocket! But just so you know Mr. PinchOfKCN's physics skills are not as awesome as those at chemistry, so please excuse me if I made any mistakes....
(The datas used in the calculations are approximate estimations, so the answers are possibly, flawed.)

time in air = 0.23s
initial velocity = 0m/s
mass of empty bottle = 1.8kg (according to a standard 5 gallon-bottle)
inclined plane angle = ~35°(okay, I REALLY took a guess)

For finding acceleration, we use the following equation:

a = g x sinΘ

Therefore = 9.8m/s (sin35°) = 5.6m/s/s

Finding how much force has been applied to the rocket:

Fa = m(a+gsinΘ)

Therefore = 1.8kg (5.6m/s/s + 9.8m/s/s x sin35°) = 20N
So the basic force that's required to shoot this rocket is 20 newtons. If an idiot was standing in front of the rocket when it is about to launch, he'll definitely gets hit in his face, right? The calculation below'll show you how much it hurts.

mass of object in motion = Fa / a

Therefore = 20N / 5.6m/s/s = 3.6kg
When an object is moving, the faster it moves, the "heavier" it gets. This 1.8kg water bottle has gained an extra 1.8kg while it's moving! Imagine the idiot gets hit by half a bag of rice...Ouchhhh!!!

Double Marriage Sets Fire To The Rain

Adele joke anyone? No? Okay.

Anyway...onto today's topic...Double Replacement

My grade 10 teacher always told me it's like your parents get divorced, and then marry your friends parents...


The General Form:
AB+CD  →  AD+CB

Rules
1. If there is a change in state there is a reaction.
2. If there isn't a change in state then there is no reaction.

How do we determine state change? I don't know...If you ask me who do I ask?

Just kidding, PinchOfKCN always has the answer (and if we don't, we actually just ask Google).

Step 1.Use your Table of Solubilities and look for the ANIONS in your reactants (not onion) in the left column.
Step 2. Look at the corresponding middle column cell to find the CATION.
Step 3. Now you should be able to find if it is Soluble or Not (Low) Soluble in the last column cell.
Step 4. If it is soluble, the product is aqueous (aq), if not soluble it is a solid (s).

There is a NET reaction when precipitation occurs. *No It does not mean rain, it means forming a solid*
The aqueous ions that are same on the both sides wipe each other out.
                          Eg.

Hey you, eyes downs here, I know this is boring and Adele's eyes are mesmerizing but we ain't done here.

I'm sure Adele knows a lot about Combustion. You know, setting fire to the...you know what nevermind.

Combustion is the a reaction when something is set on fire. In chemistry, this means reacting with Oxygen.

The General Form:
AB + O₂→ CO₂+H₂O


We'll be mostly dealing with burning Hydrocarbons (more on that later), so it makes things easy for us. An example of combustion is lighting methane(CH₄) on fire. 
CH₄ + O₂ → CO + H₂ + H₂O


On the right you'll see Charmander setting to the fire to the air.
Trivia: The fire on the tip of Charmander's tail is a measure of its life; if it goes out, it will die.



Last but not least, simple Neutralization.


Basically... acids + base > salt + water.
This is a special type of double replacement


The General Form:
HA + BOH  →   H2O + BA


An example: 
HCl + NaOH  →   NaCl + H2O

 Not one but many at the same time interesting...

I set fire to the rain!

Critically acclaimed Couple's therapy (aka Types of Chemical Reactions!)

Hello there, I'm Mr.PinchofKCN, the director of the PinchofKCN Marriage Counselling Institute. Thank you so much for revisiting our clinic today for our critically acclaimed couple's therapy course. Today's lesson, aka lesson #18, is on the "types of chemical reactions." So ladies and gents, before we get started, how are you guys all feeling today?

Types of chemical reactions! Yup that's right, that's our topic for today. Not the one you have in mind though.(You dirty-minded people,jokes!) Enough role-playing now. Let's get down to the business.

So there are 6 types of chemical reaction: production of excessive hormones... I mean, synthesis, decomposition, single replacement, double replacement, combustion, and neutralization:)

These are just basic review from Science 10, which is like what, a LONG LONG time ago. Okay, no need to panic. Let's recap. (P.S. smarty-pants are permitted to take a nap for the time being.)

Synthesis reaction is when two or more simple reactants to form a complex product.Words are always hard to understand right? Let's try some simpler form of words - letters:

                 A+B →AB

The old-school examples are always the best. When Adam and Eve come together, they become a couple, the world's very FIRST couple according to the Bible. In our modern society, Adam&Steve, Madam&Eve are all decent and acceptable examples within this context. So there you go, imagine Adam is "Aluminum" and Eve is "Sulphur". And their product, aka their offspring in this case is:

E.g. Al + S → Al2S3  ------> now balance the equation you'll get:  2 Al + 3 S →1 Al2S3

Decomposition reaction is the direct opposite to synthesis. It is when a product is being broken down into two or more simpler forms.

                 EF →E+ F

(The following examples have no direct link to the example presented above.)

Okay, so if a couple doesn't get along anymore, they would become separated. (and our world-famous couple's therapist would be more than happy to help. Please call 1-800-pinch-of-kcn to schedule your appointment today!)

E.g. H2O→ H2 + O2 ---------------------------> now balance it: 2 H2O→ 2 H2 + O2

Single replacement reaction is when one element replaces another in an ionic compound. Metals replace metals(+ ions) and non-metals replace non-metals(- ions).

             When A is a metal:                     and when B is a non-metal
             A+ BC → AC+ B                          A+ BC →  BA+ C

E.g. 2 Na + 1 H2O →1 Na2O + 1 H2 

Finally something new, smarty-pants time to wake up for some real deal.


Predicting single replacement!
During a single replacement, some metals and some non-metals are more reactive than others. Doing this types of problems require the use of a chart called the "Activity Series" to see whether there's a presence of reaction or not. (Don't get tooo excited, buddies)

-There is a reaction IF the element doing the replacing task has a higher up position in the chart than the one being replaced.
-There is NO reaction IF the element doing the replacing task has a lower position in the chart than the one being replaced. Therefore, you write "no reaction" or "NR." beside the given chemical equation.

Let's play around with an example first (Yes, that's how we roll, examples-maniac)

How you interpret this is utterly simple with our innovative and original analogy (therefore, citation to PinchofKCN is required if you wish to use the following example. I'm hella serious, my friend. wink: wink:)

Ca + HCl → CaCl2 + H2   ------> balance the equation you'll get: 1 Ca + 2 HCl → 1 CaCl2 + 1 H2

Single replacement is just like mating in the animal kingdom (or even within the human species). If you are a less preferred object, you will be quickly replaced. And if you are a more preferred object, you'll be quickly replacing other's position. Just like how Mr. Hyrdrogen is being replaced by Mr. Calcium because Mrs.Chlorine thinks Mr.Hydrogen is not "handsome enough." LOL, and that wraps up our lesson today.

Another joke about H2O, we just love water so much that we need to mention it every now and then! Enjoy!

Doesn't the old lady in the picture remind you of Miss Muriel Finster from Disney Recess. Except with a less grumpier face. And that boy sure doesn't look like T.J.

Back to some Basics (Naming and Balancing)

Good day everyone! Since we're doing hardly more than review today, we'll start off with a joke. A chemist and his dad walk into a bar. "I'll have some H₂O," the chemist says. His father says, "I'll have some H₂O too(2)". The chemist is now planning his father's funeral.

Naming
If you'll remember, all the way back here, we reviewed how to name compounds. For most of you, this should be old-hat. For our new readers, however, we'll do some review.

Ionic compounds, that is, a bonding of a metal and non-metal atom, are named simply by taking the name of the metal (attached with a roman numeral if it has multiple charges), followed by the non-metal element ending in -ide. Depending on the element, you might have to truncate the end, such as carbon→carbide.

Covalent compounds, or compounds formed from the bonds of only non-metal elements, are slightly trickier. The general method is to simply take the two elements and prefix them with the corresponding number of atoms in that compound. As with Ionic compounds, the second element should end in -ide. For example, CO₂ is Carbon Dioxide. To the right is a chart of the common prefixes.

For acids, one must remember only a simple mnemonic. "ate ic ite ous". Say it enough, it'll stick. To make sense of this, find a list of common anions. You'll find many end with "ate" or "ous". When a Hydrogen is attached in front (making it an acid), simply change "ate" to "ic" or "ite" to "ous", and smack on an "acid". If it's just a single element following Hydrogen, name it Hydro[element]ic Acid.


Naming
Now that we've gotten that annoying bit of elementary chemistry out of the way, let move on to...something equally basic. Crap. I mean, let's begin.

The essential part of balancing is just adding coefficients to molecules (or elements) on both sides of a reaction equation to make the number of atoms for each side equal. Below is an example of a balanced equation.

1Zn+2HCl→1PbCl₂+1H₂

Now in class we'll learn techniques for balancing like doing it systematically, looking at the number of atoms and such. These are good skills if you can use them intuitively, otherwise, we at PinchOfKCN offer a less arbitrary method.

This method assumes you can solve systems of equations. If you can't, well, pardon my French, but vis-vous aller apprendre un peu de maths.

For example, we'll use Fe₂O₃+Al  →Al₂O₃+Fe.


We'll break this down a bit.

And now we'll add some coefficient variables in front.
[A]Fe₂O₃  +  [B]Al  →  [C]Al₂O₃  +  [D]Fe


And to balance the equations, we just need to solve this system of equations.

If you're math savvy, you'll know that we have 4 variables and 3 equations, so this is just a bit unsolvable. How do we fix this? Well, let's just substitute a number in.

Since we have fractions, let's just get rid of those nasty denominators.

And voila, fine (pronounced [FEE-nay]).

Just before we say goodbye, let's finish the way we started; with a joke.
Argon walks into a bar. The bartender says, "I'm sorry, we don't serve noble gases here."
...
...
...
Argon doesn't react.

Good day everyone, and I sure hope you know these methods in and out now.

Molar ǝɯnןoʌ of a Gas

Hello to our fellow blog readers! Happy new year to everyone! Have you been practicing some chemistry questions during the holiday?
If you haven't, Mr.(or Miss) PinchofKCN will be very disappointed. Today we're going to talk about molar volume of a gas.
I'm sure that you must be very excited about this, because everyone wants to do as much chemistry as possible before 2012 ends.

So here's a simple yet important question to get your brain work'in before our lesson:
『What is a gas?』
No, you don't invite gases to your birthday party, and you absolutely do not want to gas the age of a woman.
A gas is a state of matter that has the lowest density of all three classic states (liquid, solid, gas). A gaseous matter is made up of atoms or molecules that can move freely under room temperature. When gases like carbon and oxygen are heated sufficiently, combustion will happen. On the other hand, when CO2 is cooled, it'll condense into water vapour(liquid).
If  you would like a recap on the three states of matter, visit our past post here.

Since gas will expand when heated and contract when cooled, their volume changed at the blink of an eye. As a result, we have to understand the STP in order to calculate its volume. I know there must be a blank look on your face, and you should be wondering what in the world does STP stand for.
STP, or Standard Temperature and Pressure, is a set of data that allow scientists to compare their measurements to the gas's properties under a temperature of 0℃.
There isn't a universally accepted STP value, but the most widely accepted one is: 0 °C (32 °F or 273 K) and 1 atm.

Now, I believe everyone's clear on the idea of STP, right? So why don't we start doing some math together?

Double Dare time:

Calculate the volume occupied by 5.8g of carbon at STP.

Step1: Memorize the magic formula
One mole of gas will occupy 22.4 litre of gas.

1 mole of gas

22.4 L of gas

Step2: Calculate the mass of carbon

5.8g x 1mole  = 0.483 moles
       12.0 g


Step3: Use the magic formula!!!

Molar Volume= 22.4 L x 0.483moles = 10.8192 L
              1 mol


Step4: Sig figs

Now look at the question again. It asks for 2 sig figs, so we should round the answer up to 11L.

Final answer: Volume occupied by 5.8g of carbon at STP= 11L.


See? You've just calculated the volume of a gas in 4 steps!!! (2 steps, actually. Excluding memorization AND sig figs.) Don't you think it is as easy as blowing a bubble with gum? Now I'll wish you a good luck because there'll be a chapter 4 test on next Thursday. Remember to re-read all of our blog posts for Ch.4 and I'll promise you an A+! :)

Oooh 10 Million Gallons Over The Sea (Spongebob anyone?)

Who doesn't like to buy things in bulk? For example,  Kellogg's cereal.

We're not going to by a flake at a time, no. We will buy boxes of them, more importantly, boxes filled with those yummy cereal flakes.

Companies that buy chemicals also purchase in concentrated, bulk form. Why is this? I just decided to trust the word of a stranger, that if chemicals weren't shipped in bulk, "we would be hauling a lot of water around."

Enough digression; let's move on to the main topic: Dilution.

If nothing else, just remember this simple formula:

M₁L₁ = M₂L₂ 
If you'll recall, M stands for Molarity, which is given as M=mol/L.
In this formula, what it's basically saying is that the number of moles before dilution, and after dilution remain the same.

Example Time!

If you have 2.00L of 16.0M HCl and you need 800.mL of 2.00M HCl, how much of the original concentration do you need, and how much water do you need? Give answers in mL.

Step 1: Write out what you have first. 16.0M HCl * L₁ = 2.00M HCl * 0.800L

Step 2: Simplify with the information you are given. 16.0M HCl * L₁ = 1.60 mol HCl

Step 3: It's basically math...we're trying to find L1 so it should look something like this...

1.60 mol HCl = L1 0.100L or 100.mL

                                                 16.0M

What's up with those trailing zeros and decimal point? Well remember our meticulous friend...significant figures.

Bonus Step: Hmm... We have the solute but we are missing something... oh right! WATER

Well Mr.PinchofKCN how do we find that? 

Mr.PinchofKCN: SIMPLE! Just subtract the L2 with L1 that we just found above.

0.800L - 0.100L = O.700L=>700.mL of water is needed!

Now, instead of my half-rate explanation, how about a real demonstration by a credible scientist? I mean, he's on YouTube; he must be credible!

That is 3 minutes and 36 seconds of my life that I will never get back...

A cat to cheer us all up!