Percent Composition Lab: Chemistry Experiment Using Baking Soda
Percent composition labs help chemistry students understand how the mass of elements relates to the total mass of a compound. In this hands-on percent composition lab, students determine the percent composition of carbon in sodium bicarbonate by reacting baking soda with sulfuric acid and measuring the carbon dioxide released.
This percent composition chemistry experiment allows students to calculate percent composition experimentally, compare their results to the theoretical value, and determine percent error. It is ideal for high school chemistry students learning percent composition, mass percent, and stoichiometry.
For the extremely busy chemistry teacher, it doesn't get much better than this for a great chemistry lab.
Imagine this:
✔ Quick setup
✔ No crazy materials
✔ Hands-on science
✔ And your students actually having fun while learning percent composition
Sounds like a dream? Nope — it's just good teaching! 😎✨
🧪 Materials for the Percent Composition Lab:
It is a good day for the chemistry teacher when these are the only lab supplies you need.
- Baking soda
- 2N sulfuric acid (which equals 1M for sulfuric acid)
- A spot plate
- A Beral pipet (or basically any dropper)
- A laboratory balance
- A test tube
That's it. That’s literally the entire supply list. 🎉
No hunting for exotic lab supplies. No prepping for hours. Just good, clean chemistry (well, mostly clean... there might be a little fizz).
🌟 What's Happening Here?
Students are going to figure out the percent composition of carbon in baking soda (fancy name: sodium bicarbonate, NaHCO₃). The percentage composition of a compound is the percentage by mass of each of the elements in the compound.
When you mix baking soda with sulfuric acid, it bubbles and fizzes as carbon dioxide gas is released. According to the Law of Definite Proportions, the mass percentage of carbon in the bicarbonate will be constant, no matter how much sodium bicarbonate is used in the experiment.
Students simply weigh out an amount of baking soda. Drops of 2N sulfuric acid are added to the baking soda, one drop at a time. The reaction releases carbon dioxide. Students continue adding drops of acid until there is no further reaction.
The mass of the apparatus is taken both before and after the completion of the reaction to determine the amount of carbon dioxide that has been released. From the mass of carbon dioxide released, students can mathematically determine the amount of carbon in the released sample, and therefore the percent composition of carbon in sodium hydrogen carbonate.
The student will determine the percent composition of carbon in sodium hydrogen carbonate, both experimentally and theoretically. The student will then determine his/her percent error.
How to Calculate Percent Composition
Percent composition tells you the percentage by mass of each element in a compound.
The formula for percent composition is:
Percent composition = (mass of element ÷ total mass of compound) × 100
In this lab, students determine the mass of carbon indirectly by measuring the mass of carbon dioxide released during the reaction between sodium bicarbonate and sulfuric acid. Using this data, students calculate the percent composition of carbon in sodium bicarbonate and compare their experimental results to the theoretical value. Students learn how to find mass percent using real experimental data, making the concept more meaningful and easier to understand.
🔥 Why This Percent Composition Lab Works So Well
- Students see the chemistry happening right before their eyes.
- It locks in the concept of percent composition.
- It reinforces the calculations that are being taught in the classroom.
- Supplies are so basic you probably already have them.
- Setup and cleanup are a breeze.
- Real data + theoretical values = perfect chance to teach percent error.
- Safety? Easy. Goggles on, and you're good to go. (Dilute acid = low drama.)
And did I mention? Students LOVE the bubbling. LOVE. IT.
You can find this lab and other related resources in my TPT store:
Don't you need you figure in the mass of the Sulfuric Acid you are adding to the reaction as well as the original mass of the baking soda so you can cancel that from the change in mass?
ReplyDeleteYes, the entire unit (spot plate, test tube containing sodium bicarbonate, Beral pipet containing sulfuric acid) is massed before and after the reaction is complete.
DeleteWhat do you mean by 2N sulfuric acid. Do you mean 2 M?
ReplyDeleteThank you for asking! I did mean 2N sulfuric acid. Normality (N) refers to equivalents of reactive hydrogen ions per liter, while molarity (M) refers to moles per liter. Because sulfuric acid (H₂SO₄) is diprotic and can donate two hydrogen ions, 1M sulfuric acid equals 2N. So 2N sulfuric acid is actually 1M, not 2M. I appreciate you checking for clarification!
Delete