The link to the answer key to your study guide was note posted correctly this weekend. I’m sorry for any trouble this may have caused your to your studying. The test is still today and the answers are now posted. Good Luck.

The Day After – The Day After – The Superbowl is our test day. I feel like we’re pretty good with Balancing Reactions (Be careful with those combustion reactions) but we need to get better at Identifying the type of reaction based on the reactants. That was the goal if the voicethread project, to review the types and make connections. Now will be your chance to prove it…

There will be a review packet on “Predicting Types of Reactions” to work on today. It will be due Friday (remember tomorrow we’re in the lab). The answers will be posted mid-day today SO CHECK YOUR WORK! Don’t just copy!

Predicting Types of Reactions.pdf

Why is it Super Week?

Well because we’re Super excited about Types of Reactions… duh. Yeah… right. Seriously though, this could be a Super Week for you. We originally had scheduled our Types of Reactions test for this coming Thursday… BUT! because we did such a great job in the lab last week, we’re going to push back the test and do another Lab this Thursday instead. So this is a look at your Super Week…

Monday  –  We’ll start our VoiceThread Review Project. Due Tuesday Night
Tuesday  –  We’ll complete our Voicethread Review Projects. Due by 11:59pm
Wednesday –  We’ll start our Review Packet with information and practice problems (Due Friday)
Thursday  –  Lab Day
Friday  – Review Day

Sunday  –  Super Day (Go Niners!)
Monday  –  Day after Super Day (No School in recognition of the Football State Championship)
Tuesday  –   Test Day ( I know, I hate tests after a weekend too. But you can use that day off to prepare)

Now, on that note, today we’ll be starting our Voicethread review projects. The link to the document is available below and on the semester 2 docs page. It is worth 20 pts and is due tomorrow before 11:59pm.

Types of Reactions VoiceThread Project

Ha Ha, very fun (*not laughing… ok, maybe a chuckle). That was not the ‘Double’ I was talking about. I was talking about Double Replacement Reactions. They’re a lot like single replacement reactions… but EASIER!

This is the basic set up of a Double replacement reaction:

2 Ionic Compounds → 2 New Ionic Compounds

Another way to visualize this would be this set up…

CationAnion + CationAnion → CationAnion + CationAnion

That’s pretty much it. Other than the subscripts, which like all Ionic Compounds are determined by the charges. Remember the rules:

• Charges are Equal & Opposite → Subscripts are 1 to 1
• Charges are Different → Use the Crossing rule

And just like that, you now know the 6 types of Chemical reactions!

We’ll be doing a Lab tomorrow and start reviewing next week. Plan on the test over chemical reactions being Next Thursday!

Today we’ll be discussing single replacement reactions. Single Replacement reactions always follow this format:

Element + Ionic Compound → New Ionic Compound + Different Element

Another way to think of them would be this…

So Here’s how it works. We’ll use the Reactants Zn + Cu(NO₃)₂ →  As our example

Step 1: Identify the element as either a Metal or a Non Metal.
–              For our reaction Zn (Zinc) is a metal. So, we’ll write ‘Metal’ under Zn

Zn + Cu(NO₃)₂ →
Metal                        –

Step 2: Determine the charge of the Element.
–              For our reaction, Zn has a charge of +2. So we’ll write that below ‘Metal’

Zn + Cu(NO₃)₂ →
Metal                        –
+2                          –

Step 3: Seperate the Ionic Compound into Cation and Anion and determine the charges
–            In almost all Ionic compounds the Cation is listed first, and it’s almost always a Metal (except when it’s ‘H’)

Zn + Cu(NO₃)₂ →
Metal   Cat.  An.       –
+2       +2     -1          –

Step 4: If the Element is a Metal then it will replace the Cation; It will replace the Anion if it was a Nonmetal.
–              For our example, Zn will replace the Cu. The other element is left standing alone in it’s elemental form.
–              Remember the charges will determine the subscripts. In this case, Zn has a charge of +2 and since NO₃ has a charge of -1, it takes 2 NO₃‘s to make the charges balanced.

Zn + Cu(NO₃)₂ →   Zn(NO₃)₂  + Cu
Metal    Cat.  An.                                –
+2         +2     -1                                 –

That’s all folks.

Seriously though, we’ll be talking about Combination reactions today and believe it or not they’re not that bad. Let me show you.

Combination reactions always follow this pattern:

1 Compound + H₂O → 1 Compound

They’re really easy to balance, but you have to know which type of combination reaction you’re working with before you can start.

1. Metals – If the compound in the reactants is a metal and Oxygen, these are the steps you follow:

1. You must determine the charge of the metal. To do this, separate the compound and use your periodic table or the crossing rule (If the compound has subscripts, that may be the charge of the opposite atom). Lets look at this example:

CaO + H₂O →
↓   ↓
+2  -2

          Looking at the periodic table we see that Ca has a charge of +2 and O has a charge of -2

2. Now that we know the charge of the metal, we “Combine” that metal with Hydroxide (OH-). The number of hydroxides is determined by the charge of the metal.

CaO + H₂O →  Ca(OH)₂
↓   ↓                      ↑      ↑
+2  -2               Ca+2  (OH)-1

In our example, we need 2 (OH) ions to balance the -2 charge of Ca

3. That’s it! It’s that simple. And all you would have to do now is balance but even that is pretty easy. In fact, this one is already balanced!

1. Nonmetals – If the compound in the reactants is a Nonmetal and Oxygen, these are the steps you follow:

1. When a nonmetal oxide reacts with water it forms an Oxoacid (Remember, oxoacids start with H and end with a polyatomic ion). So to do this you simply add all the H’s, add all the nonmetal atoms, and add all the O’s. Those numbers become the subscripts of your Oxoacid. For example:

CO₂ + H₂O →

Just add the H’s (2), the non metal in this case is C (1), and the O’s (3). Then combine them into one Oxoacid:

CO₂ + H₂O → H₂CO₃

DONE! HOW EASY WAS THAT!

The only exception would be if the answer does not have a Polyatomic Ion, but the subscripts all have a common denominator, you make the common denominator the coefficient and reduce the subscripts. For example:

N₂O₅ + H₂O → H₂N₂O₆

Well there is no Polyatomic Ion that is N₂O₆ But all the subscripts are divisible by 2! So 2 becomes the Coefficient!

N₂O₅ + H₂O → 2 HNO₃

So that is Combination Reactions. Hope you learned something and don’t end up like this guy…

Alright after a long break between posts, lets review what we have covered thus far…

1. Reading and Writing Reactions – Voicethread

Example: N₂ (g) + 3H₂ (g) → 2NH₃(g)

To read or write out a reaction, we will first describe each part of the reaction. To do that you follow these rules:

1. Each atom, molecule, or compound is described in moles. (If it is an atom, you describe it as “Elemental”; if it is a compound, you describe it using the proper name from our last unit)
2. The Coefficient is equal to the number of moles of that substance
3. To finish the statement, the state of matter is used.
4. Each part of the reaction is connected to the others by a descriptor, which represents a symbol from the reaction (i.e. “Reacts with” & “To Form”)

So for the example listed above it would read as follows:
1 mole of elemental Nitrogen gas
Reacts with
3 moles of elemental Hydrogen gas
to form
2 moles of Ammonia* Gas (the * means it has a special name)

2. Balancing Reactions – Voicthread

To balance a reaction means to have equal parts, or each type of element, on either side of a reaction. The easiest way to do this process is by showing your work! Here’s how we do it:

Example: Ca₃(PO₄)₂ +  C  → Ca₃P₂  + CO

Step 1:  list all the elements shown in the reaction below the reaction Arrow

•                                  Ca₃(PO₄)₂ +  C  → Ca₃P₂  + CO
•                                                         ____  Ca ____
•                                                          ____  P  ____
•                                                          ____  O ____
•                                                          ____  C ____

Step 2:  Write the number of each type of element, from that side of the reaction, on that side of the symbol.

•                                                                                Ca₃(PO₄)₂ +  C  → Ca₃P₂  + CO
•                                                                                                          _3_  Ca _3__
•                                                                                                         __2_  P  _2__
•                                                                                                         __8_  O _1__
•                                                                                                         __1_  C _1__

Step 3:  In order to make the numbers match on either side you can change the number of any type of element by changing the Coefficient of that element or molecule. You cannot ever change the subscripts. Changing the coefficient of a compound effects all of the elements in that compound.

•                                                                                Ca₃(PO₄)₂ + 8 C  → Ca₃P₂  + 8 CO
•                                                                                                          _3_  Ca _3__
•                                                                                                         __2_  P  _2__
•                                                                                                         __8_  O _1_8
•                                                                                                         8_1_  C _1_8

Important: If there is more than one of the same type of element on one side of the reaction arrow, you must add them together

3. Types of Reactions – Voicethread

There are 6 types of reactions. Knowing the type of reaction that will occur based on the reactants, allows us to predict the products. Here are the three types we have discussed and how to predict the products (Important: These reactions are not balanced. You must determine the products before you can determine the reactions)

Synthesis: Element + Element → 1 Ionic Compound

The important step when doing synthesis reactions is to determine the ionic charge of the reactants.

If the charges are the same → The subscripts of the elements in the compound are 1 to 1

Ca    +    S₈     →    CaS
+2          -2

If the charges are different → Use the crossing rule (the charge of one, becomes the subscript of the other

Zn    +   N₂  →    Zn₃N₂
+2         -3

Decomposition:  Compound  → Element + Element (+ Element …)

The important step when doing decomposition reactions is to determine Elemental State of each element. If it is Diatomic, it always has a subscript of 2, if it’s tetraatomic, it always has a subscript of 4, if it’s octoatomic it always has a subscript of 8.

Ca₃(PO₄)₂  →   Ca +     P₄ +     O₂

Combustion: Hydrocarbon + O₂  → CO₂ + H₂O

That’s it. As long as a compound that contains Carbon & Hydrogen reacts with Oxygen, the products will ALWAYS be Carbon Dioxide and Water. As easy as that sounds, these are the problems that are difficult to balance.

So that’s 2 weeks of work in a nutshell. We’ll continue on the other 3 types of reactions in the near future. AND, hopefully get into the lab sometime soon as well. Watch the voicethreads for more in-depth understanding of what we are covering! Good Luck!

Welcome back to the end of the first semester. Yes it seems odd to be back from break and still in the first semester, but today provides a good opportunity to reflect on what we have accomplished and where we are headed.

Today you will be completing the following in your abbreviated class period:

1. Review your exam grade, quarter 2 grade, and semester 1 grade. If you find an irregularity, please email me or find Mr. Fogel (I will not be in the building today)
2. Clean out your folder/binder of all non essential materials (keep ALL NOTES, class rules, and lab safety info)
3. Obtain a review sheet from the cart of important topics or rules we have learned from this semester that we will need to have for next semester.

Have a great day and I’ll see you Next Semester!