Acid-Base Titration of an Eggshell
Summary
In this lab, students are scientists from the Department of Agriculture and presented with the problem that a farmer has brought to them. The farmer contends that his hens' eggs haven become more fragile over the past ten years. The farmer believes the problems are due to illegal dumping of PCB's and other chemicals that hinder the hens production of calcium carbonate.
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Learning Goals
The goal of this activity is to calculate the amount of calcium carbonate present in an eggshell, use titration measurements to make conclusions, and apply stoichiometry concepts to infer conclusions.
Context for Use
This is a lab that with proper pre-lab work can be completed in a 50 minute class period, but can be adapted to complete the drying in one day and the lab the next day.
Special equipment: drying oven
Special equipment: drying oven
Description and Teaching Materials
In this lab, students are scientists from the Department of Agriculture and presented with the problem that a farmer has brought to them. The farmer contends that his hens' eggs haven become more fragile over the past ten years. The farmer believes the problems are due to illegal dumping of PCB's and other chemicals that hinder the hens production of calcium carbonate. Eggshells from the farmers hens contain about 78% calcium carbonate by weight. The calcium content of a normal eggshell can be easily be determined by means of an acid-base back-titration. Lab Procedure (Microsoft Word 14kB Sep17 08) Materials Sheet (Microsoft Word 2007 (.docx) 10kB Jun3 11)
Teaching Notes and Tips
Experiment works best if the eggshells are dried overnight, so students are not rushed to complete the lab in 50 minutes.
Assessment
Lab report should be created individually by students, complete with analysis and conclusion.