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Acids & Bases -- Arrhenius definition and pH

4/13/2014

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There are several theories defining acid and base formulas and today I'm going to focus on the Arrhenius definition and the commonly used pH scale.

Objectives:

1.  Define and give examples of Arrhenius acids and bases; classify a solution as neutral, acidic or basic, given the hydronium-ion or hydroxide-ion concentration.

2.  Calculate the pH or pOH of a solution given the hydronium-ion or hydroxide-ion concentration.

3.  Calculate the hydronium-ion or hydroxide-ion concentration given the  pH or pOH.


Here is a brief overview (3+ minutes) of the Arrhenius definition of acids & bases:
The Arrhenius definition is essential to the idea of pH and its companion pOH -- here's an overview.  There is a little bit of extra dialogue, but overall it has the essential information:
I like his brief "ode to Jimi Hendrix" -- heehee. 

This next video slows down to get into the math associated with pH and pOH:
I like that he mentions that there is more than one way to get the answers.  It's a nice way to check yourself, too!

Notice that he guides students through using their calculators to perform calculations with scientific notation -- I've included that in my lectures to students b/c they tend to enter "x 10" to a power versus using the EXP or EE buttons on the calculator, ending up with an answer higher by 1 power of 10 -- help your students avoid this!

Here are a few worksheets practicing pH/pOH problems:

http://chemistry.about.com/library/pdfs/acidbase.pdf

http://misterguch.brinkster.net/PRA027.pdf

I will be relating pH/pOH to Ka and Kb in my next post.

Check out my lab book "Chemistry on a Budget" at amazon.com:
http://www.amazon.com/Chemistry-Budget-Marjorie-R-Heesemann/dp/0578129159/ref=sr_1_1?s=books&ie=UTF8&qid=1389410170&sr=1-1&keywords=chemistry+on+a+budget

Each lab is presented with two possible report formats -- both labs use the same procedure page but each has a different conclusion page -- one with 10 questions to be answered as a conclusion, the other with a full laboratory report required.  This gives the teacher the option of what type of report is desired!  

I have a few links listed under Teaching Resources that could be very useful -- if you haven't checked it out, the link is at the top of this page!  I just added one that has several Powerpoint presentations that you might find useful.

*I'd love to hear from you!  Your feedback would really help me to focus on your needs. You might have had a school vacation around now  are around this time) -- take advantage of the time and write me about your classroom experiences!  There should be a "Contact" form below, or click on the "Contact" tab on the top right of this page.  

Have a good week!


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    Marjorie R. Heesemann is a chemistry teacher with 15 years of experience who is now working to develop resources for the Chemistry classroom.

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