This experiment is for advanced students. This lab builds on concepts from the previous carbon dioxide lab.

Limewater….carbon dioxide…indicators. We don’t know too much about these things. Sure, we know a little. Carbon dioxide is exhaled by us and plants need it to grow. Burning fossil fuels produces carbon dioxide.

Indicators…something we observe that confirms to us that something specific is happening. Lime water turns cloudy and forms a precipitate in the presence of carbon dioxide. Blue litmus paper turns red in the presence of an acid. The dog barking at the door and dancing around indicates that you better let the dog out, and quick, to avoid….a pet spill?

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Materials:

• Limewater from a previous lab (MSDS)
• One-hole rubber stopper
• 90⁰ bend glass tubing
• Test tube rack
• 2 Test tubes
• Sodium hydrogen sulfate (NaHSO₄) (MSDS) Sodium hydrogen sulfate is very toxic. Respect it, handle it carefully and responsibly. Do not take it for granted.
• Sodium carbonate (Na₂CO₃) (MSDS)

NOTE: Be very careful when handling the sodium hydrogen sulfate – it’s highly corrosive and dangerous when wet. Handle this chemical only with gloves, and be sure to read over the MSDS before using.

When pouring our limewater into the test tube, be careful! Limewater is dangerous to your skin and your nasal passages. Pour just the limewater into the test tube, not any solids that may have gotten into the limewater container.

A chemical reaction will occur between sodium hydrogen sulfate, sodium carbonate, and water. We could have used any combination of chemicals for this lab that will produce carbon dioxide (CO₂), but these chemicals are already in our kits, so……

The reaction will create a gas, that gas, we think, is carbon dioxide. If we are right, we will be bubbling CO₂ gas into lime water. If we observe the limewater becoming cloudy and if a precipitate forms on the bottom of the test tube, that is a positive indicator that CO₂ is present.

C3000: Experiment

Download Student Worksheet & Exercises

Here’s what’s going on in this experiment:

Some combination of chemicals will produce carbon dioxide –> CO₂ + ?

Notice that specific chemicals are not in the chemical equation? The actual chemistry of the chemical reaction is not our focus in this lab. We want to experience how an indicator can test for a particular compound or element.

Instead of sodium hydroxide and sodium carbonate and water, we could choose to combine vinegar and baking soda for example. Even simple household supplies can be chemicals for our experiments.

Cleanup: We are going to clean everything thoroughly after we finish the lab. After cleaning with soap and water, rinse thoroughly. Chemists use the rule of “three” in cleaning glassware and tools. After washing, chemists rinse out all visible soap and then rinse three times more.

Storage: Place cleaned tools and glassware in their respective storage places.

Disposal: Liquids can be washed down the drain. Solids are thrown in the trash.

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