Week of 1/6

Thursday (1/2): Today was our first day back from break and we started with a Standardization lab.  I explained why you need to standardize NaOH solutions and then you guys practiced performing titrations with an indicator, rather than a pH probe as in Ca(OH)2 Ksp lab.  Homework was to read the Half titration lab.  Oh, I also put the derivation of the Henderson-Hasselbach equation on the board so that you would know where it came from (part of the Half titration lab).

Friday: Snow day.

Monday: Performed the Half-Titration lab and completed analysis.  UNIT OUTLINE

Tuesday: Had a 2 hour delay b/c of severe cold. Some kind of polar vortex! We had 30 minutes to learn Salt Hydrolysis.  We did a quick lab where you added NH4Cl, NaHCO3 and NaCl to water to see that it changes the pH.  The point was for you to see how the pH can change when you put something in it that doesn’t appear to be an acid or base at first.   I then explained how this happens.  HEre’s the notes. Worksheet.  Note to self.  Everyone is totally confused by symbols. Maybe skip this until later in the unit next year.

Wednesday: Salt Hydrolysis notes.  We went over everything to do with salt hydrolysis – specifically the math, the symbols, etc.  Here’s some more organized, concise notes on Salt Hydrolysis.

Thursday:  We started with a review of salt hydrolysis – determining if a substance will be acidic or basic and how to calculate pH.  I don’t have digital copy of worksheet…Sorry, E! You might be able to figure it out from answers that start on page: 8 of the notes.  Then I did the buffer demo you can see here (if you scroll down till the picture of 4 beakers w/ green a blue solutions).  We went through a pretty simple buffer example and I handed out this worksheet for worked solutions and more practice.  Homework was from unit outline.  Here’s a video on calculating pH for buffers. There’s more videos on the Unit 7 page on this blog.

Buffers – Calculating pH from Frances Fullerton on Vimeo.

Friday: Went over how to apply Henderson-Hasselbach to buffers.  It makes it so easy! Rest of class was a work period.