Redox Reactions

Redox reactions are the last reactions we will study in this unit. It encompasses synthesis, decomposition, and single replacement reactions. It is categorized by all reactions that involve in a transfer of electrons.

• If the element/compound loses electrons, it is oxidized (because the charge becomes more positive)
• If the element/compound gains electrons it is reduced (because the charge becomes more negative)

Always Remember OIL RIG!!!

Oxidation Is Lost

Reduction Is Gained

OIL RIG

The "lost" and "gained" refers to the electrons

• Also, to make things more confusing, the compound/element being oxidized is referred to as the reducing agent
• The compound/element being reduced is referred to as the oxidizing agent
• Just think about what that compound/element is doing to the other compound/element
• To determine the oxidation number of the element use these rules:

Single Replacement:

• Always follows this structure:

• The completion of the reaction is based upon the reactivity of the elements

  

  If the element is less reactive than the element it is trying to "replace" in the reaction, the reaction will not be completed

• Nonmetals replace nonmetals and metals replace metals
• For example:

  

  The Fe (a metal) replaced the Cu (a metal) to create FeSO4
  
  

Synthesis:

• Follows this structure:

• For example:

The H2 combines with the O2 to form H2O

Decomposition:

• Follows this structure:
  
• For example: 

  

  The H2O decomposes into H2 and O2

Bozeman Science Redox Reactions Video

Acid-Base and Double Replacement Reactions

This unit focuses on chemical reactions, and the chemical reactions that we have learned so far are acid-base and double replacement. Acid-base, obviously deals with reactions with acids and bases that form water and a salt as a product. Double replacement reactions deal with aqueous ionic compounds that form solids as products.

Acid-Base Reactions:

• An acid and a base are placed together, and they react to neutralize the acid and base properties, producing a salt
• A typical acid-base reaction consisting of both a strong acid and a strong base looks like this:

HCl (a strong acid) combines with NaOH (a strong base) to form water and NaCl. In this reaction, the reactant cations switch to form the products.

• When the acids are weak, they do not disassociate in the reaction when showing the complete ionic formula of the reaction, but they do give off enough H or OH to react and form water as a product.
• Weak acid+strong base will always have the structure of:

 HA+OH-->H2O+A

Strong Acid Rules and Examples:

• HCl (hydrochloric acid)
• HBr (hydrobromic acid)
• HI (hydroiodic acid)
• Any acid where oxygens outnumber hydrogens by two or more (ex. HClO4)

Strong Base Rules:

• Cations from group 1 or 2
• All bases have an -OH anion

Common Weak Acids:

• HF (hydrofluoric acid)
• HC2H3O2 (acetic acid)

Crash Course Acid-Base Reaction Video

Double Replacement Reactions:

• Follows this format:

• The driving force is the production of a solid, so if no solid is formed, it is not a completed reaction.
• Can determine if products are solid using solubility rules

Ba and Mg are the cations, and they switch places to create the products.

Crash Course Double Replacement Reaction Video

Helpful Links:

Acid-Base Reaction Notes

Double Replacement Reaction Notes

Solubility Lab!

This lab was fairly simple, and was interesting to see how accurate the predictions I made last night on the chemical reactions were. We had mix drops of different chemicals together to see which one's reacted or not. The only difficulty in this lab was the time constraint, but my partner, Lindsi, and I managed to finish in time.

The lab set-up

Some of the reactions we saw formed (the colors were really pretty!)

The (Impossible) Solubility Rules

Last night, I had to memorize the solubility rules for the lab today, and it was awful and hard to memorize at first. I found that it became much easier after doing many practice problems for the lab. This is one of those concepts where I need to memorize and practice a lot before it becomes ingrained into my mind.

I used this chart because I left my hand-out from Mrs. Frankenberg at home.

Solubility Rules Mnemonic Device Video

New Unit! Balancing Equations

Today marked the first day of the new unit: Chemical Reactions. We did balancing chemical reactions today, and it was mainly review from physical science. It's another math based chemistry unit, but I don't think it will be as heavy handed in math as it was during Chemical Composition.

Steps for balancing combustion equation:

1. Find products (should always be CO2+H2O for combustion reactions)

2. Balance carbon

3. Balance hydrogen

4. Balance oxygen last

5. Reduce all coefficients if necessary

6. NEVER change subscripts for balancing equations

Guide to physical states:

s- solid

l- liquid

g- gaseous

aq- aqueous solution (stuff dissolved into the solution)

Diatomic Elements:
hydrogen H
oxygen O
fluorine F
bromine Br
iodine I
nitrogen N
chlorine Cl

H O F Br I N Cl (Hoffbrinkle)
DON'T FORGET DIATOMICS!!!!!!! THEY ALWAYS APPEAR IN PAIRS!!!!!!

Great website for practice problems:
http://www.sciencegeek.net/Chemistry/taters/EquationBalancing.htm

Bozeman Science Balancing Equations Video

Chloride Lab

Almost everyone in class made it to lab! The pre-lab was only one question and it was a little easier than before, mainly because we are more used to these type of questions now. Overall, this lab was less strenuous to complete. It was similar to the hydrate lab except we weren't allowed to use Bunsen burners this time.

Heating the test sample on a hot plate

Finished product (ours was a little black and crusted and I was afraid at first because no one else's looked like ours)

Cooling the finished product so we can weigh it

x_x

The test today was death. The common consensus was that everyone either failed or didn't finish...which is basically the same thing. Before the test started, Mrs. Frankenberg told us to start as soon as we can because we would need the extra time, and she was so right. The questions themselves were things we had gone over before, but doing 36 questions that each took about 3-5 minutes to finish in a 50 minutes class period was the most challenging part. Throughout the day I heard people in the halls talking about the "36 questions" and how much it sucked, and I can say that I agree with them. It sucked. every class I went into someone was talking about the chemistry test, either panicking about taking it next hour or talking about how much they failed. I'm glad it's over, but I'm dreading seeing my grade because I am so unsure of myself with this one.

Quiz- Moles, Hydrates, and Stuff I Didn't Know

The quiz today was difficult, and admittedly, I had forgot that I even had a chemistry quiz today. Coming into class, and seeing the desks turned in test formation made me panic a little, but I remembered that I was fairly confident on this material and reassured myself that it would easy... but I was so wrong. The first question took me about ten minutes to figure out, and that didn't help my confidence for the rest of the test. I soon skipped the first question and went on to the next few problems only to find that they were difficult as well. I knew from then that this quiz was much harder than I anticipated. After the first few questions of panic, I flipped over to the next page and found they were slightly easier, and was able to finish the quiz on time, but I still had that added test stress that I only get when I feel like I'm not as confident with my answers as I should be. Overall, I feel anxious about receiving my score, and I am anticipating a lower than average grade.

Hydrate Lab Fun

Yesterday, we did the Hydrate Lab. It consisted of a lot of measuring, burning, and fanning. First we weighed our test tube, filled it with a small amount of copper (II) sulfate. We heated the copper (II) sulfate with a Bunsen burner until it turned white and all of the water was driven away. We then cooled the test tube, measured it again, and then burned it again, repeating the rest of our procedure one more time to ensure that all of the water was driven away. Finally we calculated the mole amount of water that was driven away in the heating through mole conversion and dimensional analysis. The lab itself was not especially stressful, but the pre-lab certainly was. My lab partner, Lindsi, and I had to choose either problem A or problem B without knowing what each problem was. I ended up getting the easier procedure problem while Lindsi ended up with the math problem. I had faith in her to get the answer correct, but the only thing I was worried about was time. Mrs. Frankenberg gives us three minutes to complete the question, and that ticking clock adds a lot of stress that can make it hard to calculate. Lindsi got the question right, and I was not especially surprised because I knew she prepared. The rest of the class hour went smoothly, and we were able to finish the lab before the class hour finished.

The hydrated copper (II) sulfate in the test tube

After heating the copper(II) sulfate, it started to turn white

Once the copper (II) sulfate turned white, we had to fan the test tube to cool it down

Finished product

Mole Conversions Bozeman Science+ New Study Links for Chemical Composition Unit

I love this study video. Bozeman again is my lifesaver. 

Lab tomorrow... I will be studying my lab procedure.

(Updated) Other helpful links:

Hydrate Calculation Practice
http://www.chemteam.info/Mole/Determine-formula-of-hydrate.html

Mole Conversion Tips
http://www.dummies.com/how-to/content/mole-conversion-tips-for-chemistry.html

Mole Conversion Practice Problems
http://www.sciencegeek.net/Chemistry/taters/Unit4GramMoleVolume.htm

Mole Roadmap+Sample Problems
http://www.ck12.org/book/CK-12-Chemistry-Concepts-Intermediate/section/10.9/

Empirical Formula Practice Problems
http://chemistry.about.com/od/chemistry-test-questions/tp/Empirical-Formula-Practice-Test-Questions.htm

Molecular Formula Practice Problems+Answers
http://chemed.chem.purdue.edu/genchem/probsolv/stoichiometry/molecular2/mf2.4.html

New Unit! Molar Mass Conversions

Today, I realized I had predicted correctly in thinking this unit will be more difficult than the past. We had our lecture today on molar mass conversions, and I am not entirely comfortable with this whole concept partially because it is new and partially because it is a more difficult concept to grasp. Mrs. Frankenberg gave us a flow chart that is extremely helpful in learning this concept that I have here:

This picture is really cute, but I have to admit that moles are pretty ugly. You can barely see its eyes, just like me.

Chemical Composition Pre-Test :(

I was completely lost while taking this pre-test. I didn't understand the terminology or how to do the calculations, and I noticed almost all of the questions were math computations. Last test with math computations was a little rough, so I'm going to have to prepare a little more. I also just found out this unit test is the day after I get back from Youth in Government. It's far away, but I need to make sure to keep up with my schoolwork and study in advance.

There were a lot of questions involving moles, I wish I knew 6.02 x 10^23 before I took the pre-test :(