Balancing Redox Equations

Balancing Redox Equations
Scribe Post by Juliette O. (Quarter 4)
5/7/14

Agenda

First, we checked in the homework due today, the three page Electrochemistry worksheet. We then picked up three worksheets for homework, "Forming Ionic Compounds" and "Balancing Redox Equations." Then we went over the Electrochemistry worksheet. Finally, we took notes on Balancing Redox Equations in Acid-- these notes are posted on moodle. A video going over the notes will also be posted on moodle. 

Introduction

Mrs. Friedmann apologized that the tests have not been handed back yet, however she said the grades so far are quite poor. While it is the end of the school year, Mrs. Friedmann urged us to push through and continue to put in consistent effort to hold on to our grades. She reminded us that understanding homework is invaluable for the test. She also said that there will be an opportunity to make up some points tomorrow.

Homework Check

We went over the Electrochemistry worksheet in class today. 

Remember:

• Assume oxygen is not peroxide when you see O2-- assume the oxygen has an oxidation state of -2. 
• When asked to determine oxidation states of reactants and products of a reaction, start by tallying the oxidation numbers. For instance, in 2a, the substance oxidized in S in H2S, not S-2, because S is not an ion. Just because there is a -2 oxidation state does not mean there is a -2 charge--oxidation state and charge are not the same!  
• Remember, the chemical that contains the thing that is being reduced is the oxidizing agent.
• In 2d, remember that if there are 3 reactants on one side, you can identify what substance is being oxidized/reduced by identifying the oxidation numbers and seeing if there is a change in oxidation state. If there is a change in ox. state, the substance is oxidized or reduced. 
• Acronym to remember: LEORA GEROA 

Notes

See moodle for notes and a video going over the notes is also posted.

Link to Notes: http://gbs-moodle.glenbrook225.org/moodle/file.php/12015/13_14_Unit_11_--_Redox/Unit_11_Notes/3_Class_Notes_5.7.14.pdf 

Link to Video: http://vimeo.com/94433376

Homework

• 2 worksheets: Forming Ionic Compounds and Balancing Redox Equations (#1 and 3 in notes) Link: http://gbs-moodle.glenbrook225.org/moodle/file.php/12015/13_14_Unit_11_--_Redox/Unit_11_Handouts/5.7_Balancing_Redox_HW_1.pdf
• 4 Webassigns have been opened that are due over the course of the unit, the first due next week. Read ahead and use the text to finish the web assigns. W.A. due dates: May 13, 14, 19, 20

Class Blog 5/6/14

Half Reactions 5/6/14

Hello! today we started in class the homework, which was the chapter 4.4 worksheet and the Oxidation numbers worksheet. For homework tonight we have the three worksheets on Electrochemistry, found here. 

And here are two funny chem jokes. Please enjoy.

Today was a notes day in class. We followed Mrs. Friedmann as she took these incredible notes. 

The five main questions that need to be asked before determining Oxidation numbers are:

1) Is the substance an element

2) Is the substance ionic?

3) If ionic, are there monatomic ions?

4) Which elements have specific rules?

5) Solve for whats left!

I was very confused with Oxygen, as I am sure many others are. The Oxidation # for the Oxygen atom is almost always -2. Only when the charge for Oxygen is -1 and combined with another Oxygen atom (O2) is the Oxidation number -1. Ex: H2O2, Na2O2

Hope this helps!

Next Blogger: Juliet O.

Intro to Oxidation/Reduction Reactions - Monday May 5

To start off class, Mrs. Friedmann handed out three different worksheets. The first was a calendar for our LAST UNIT!!!! And the other two were worksheets we have to do for homework tonight.
    Mrs. Friedmann suggested reading chapter 4.4 in our book to help us fill out the reading sheet and complete the problems on the Oxidation Numbers worksheet.

Here's photos of the worksheets just in case she doesn't post them (and yes, they're due tomorrow):

But before you get started on these, read the the following notes that Mrs. Friedmann gave to us in class, as well as section 4.4 in the book:

Okay, to explain a couple things, the statue of liberty part is in my notes because Mrs. Friedmann used it as an example. See, the original statue was made of bronze, which we know is a reddish/brownish color right? Then how come the current statue is green? Well, that's because the outer layer of bronze on the statue reacted with the oxygen in the air, causing an oxidation reaction to occur in which the bronze lost electrons, causing it to actually turn into a different substance (just on the surface though). This is actually a good thing because now this new outer layer (which is no longer bronze and appears green) serves as a protective coating for the bronze interior of the statue.

And LEO and GER are just mnemonics for remembering that:
When molecule Loses Electrons it is Oxidized and
When a molecule Gains Electrons it is Reduced. (LEO the lion goes GER)

That's all! And the next blogger's Kevin Mihelic.

Acid-Base Titration Lab

     Today we did the titration lab demonstrated by Mrs. Friedman yesterday. Today's NaOH molarity was different than the demonstration and we were to do three trials and remove any results that were obviously deviant from the rest and then find the average molarity. A write-up is not necessary for this lab.

Here is the data for the lab:

Molarity of standard base used: 0.149M

Trial 1: 

HCl volume

• Initial- 10.4
• Final- 20.5
• Used- 10.1

NaOH volume

• Initial- 0.3
• Final- 14.2
• Used- 13.9

Molarity of acid- 2.05

Trial 2:

HCl volume

• Initial- 27.0
• Final- 37.0
• Used- 10.0

NaOH volume

• Initial- 27.3
• Final- 41.0
• Used- 13.7

Molarity of acid- 2.04

My third trial deviated from 1 and 2

--

The homework is to study for tomorrow's test. There will be a study session at 7 tomorrow.

The next blogger is...

Kevin M.

Titrations and More!

Tuesday and Wednesday April 29-30 2014

What we did in class (29th):

• Today in class we finished the indicator lab
• We went over the things that were due on THURSDAY for the lab
• Mrs. Friedman showed us an example problem that would have to do with the homework

What is due for the Lab:

• The Lab is due THURSDAY
• You need a typed data table, it's not required that the calculated pH's be on the type table
• You also need a sheet with all of the calculations required
• You need to do calculations for the following:
• .001 M HCl
• .001 M NaOH
• .001 M Acetic Acid
• .001 NH4OH
• .1 M NaCl
• .1 M Na3PO4

For Extra Credit you could do calculations for .1 M NaHSO3 and .1 M NaHCO3

Other Homework:

• The last two sheets of the packet on Acids and Bases
• This includes the two ICE Table questions on Buffers (which are done exactly the same way as common-ion problems) and the last sheet which is a general practice of ICE Tables
• These sheets are due WEDNESDAY

What we did in class (30th):

• We went over the last two sheets of the acids and bases packet
• Mrs. Friedman's computer crashed (condolences)
• We took notes on Neutralization Reactions and Titrations

Neutralization Reactions:

Acid + Base ---> Salt + Water

Ex. HCl + NaOH ---> NaCl + H2O

For every mole of H+ or H3O there should be one mole of OH to neutralize it = Titration

When you know the concentration of a base, you can find the concentration of the acid using Titration

Equivalence Point: When moles of H+ = moles of OH- = pH of 7

End Point: When the indicator is at it's faintest color possible

Overshoot: When the indicator color is too strong, you passed the end point

Calculation for Concentrations:

# of H's in the formula x Molarity of Acid x Volume of Acid = Molarity of Base x Volume of Base x # of OH-'s in the formula

Homework due Thursday:

• The lab as mentioned above
• Two practice problems that are on one of the lab sheets we received today

Next Blogger: Colin Samuels

Quiz Review

Friday, April 25, 2014
Blogger: Serene P.

Today, we began class with completing a worksheet in a group. It covered questions similar to the quiz we took on Thursday. Later, we went over the answers to this worksheet. To Georgia, Cameron, Juliette, and Hayden, you all will have to complete this worksheet when you return. 

After completing that worksheet, we made corrections to the quiz we took on Thursday. It was not taken for a grade since many people did not do so well. 

Homework:
There is one worksheet that has a problem similar to the worksheets that we were going over in class.
Also, there is a webassign that I believe is now due Monday. 

The next blogger is Daniel W. 

Quiz

April 24, 2014
Blogger: Serene P.

Due to the Juniors testing, we all had shortened periods today. Ms. Friedmann had us check in our homework on pages 10-11 at the start of class. Afterwards, we took the quiz that was over those pages. We did not go over the homework. 

Homework:
There is a webassign due Sunday night at 11:59 PM. 

I'll blog tomorrow as well.