Strong Acid / Strong Base Titration pH Calculation Practice

The Case of the Missing Data and the Dishonest Chemistry Students!

In the past, I’ve lectured on this SASB titration pH calculations, then because of time constraints, students had little to no time to actually practice it themselves. This year, I finally got around to creating a flipped classroom video of how to do these calculations, which freed up time for me to actually have them do something with it!

Before Class
(introducing SASB Titration & pH Calculations)

Before my students came to class, they watched these two videos I made and took notes on this notes sheet. The first video introduces what titrations are and show particulate diagrams at each stage. The second video shows how to calculate pH at each stage of the titration curve. After watching the videos, students had an idea of how to all of this, as well as a record of it in their notes, but…it’s a lot. They still needed (of course) a lot of practice.

This is a video I made back in 2016. I think my video skills have improved a lot since then…

The Assignment
(The Case of the Missing Data & the Dishonest Chem Students)

I immediately started class by presenting this task, also embedded below.

The basic premise is that they had all this titration data from a lab last week, but they lost the Vernier Graphical Analysis file and now have to create some fake data to fool their unsuspecting teacher.

Pretty silly, but I played it up a bit, going as far as putting the base volume on a sticky note in one member of each group’s lab book, pretending they wrote it themselves.

The purpose of this task is to get students creating the titration curve and doing all the pH calculations themselves. Instead of a list of problems, they’re doing the calculations in the context of the titration curve as a whole, creating as many data points as possible in the ~1 hour they had to work on this.

Student worked in small random groups of about 3 or 4 at vertical whiteboards (a la Building Thinking Classrooms principles, which I use in my classes) to calculate the initial acid molarity and the pH of points along the graph.

This group, which calculated the most data points, used the same Before/Add/After table and just kept changing up the numbers. It was a great way to sort of automate the process and get quicker results.


Here are the graphs that each group produced. I was pretty happy with it overall. The first group, at least, could have fooled me with their graph, haha!

This group rocked it. They found pH every five mL, then went back and added some more points near the equivalence point to show how that section curves.
This group did pretty well too. Something went wrong in their calculations past the equivalence point, but we ran out of time to figure out what the mistake was.
This group took the longest, but they at least got practice calculating pH. I’m not sure why they didn’t include the equivalence point pH of 7, but I’ll follow up with them next class.

I’ll definitely do this again next year. The main thing I’ll change is to have them include a particulate diagram at each stage of the titration curve.

2 thoughts on “Strong Acid / Strong Base Titration pH Calculation Practice

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