Gas Absorption by Water
Acid rain is created when water droplets in the air absorb the pollutant gases known to create sulfuric and nitric acids. This lab will demonstrate the gas known as carbon dioxide being absorbed by water and changing the physical property known as pH.
50 mL beaker
pH strips / pH color chart
1. Place a small sample of water (approximately 20ml) in the beaker. Test for
and record the pH value.
2. Place straw in water sample and exhale gently into water for
several breaths—at least a minute.
3. Measure the pH of the sample again and record the value.
4. Compare with previous reading.
5. Answer conclusion questions.
**Save water sample for use in the “Extension Exercise”!! (found after conclusion section)
Sample after exhaling
- What happened to the pH value of the water?
- What two chemical compounds interacted in this lab?
- How does this experiment resemble what occurs when acid rain is created?
BONUS: What two pollutant gases are the largest contributors to the creation of acid rain?
Using the water sample left over from earlier in this experiment, you will now attempt to neutralize the water again. Do this by adding very small amounts of baking soda to the water. Stir it until dissolved each time you need to add some and then test the pH to determine if you need to add another small amount. Continue doing so until you reach a pH of at least 7. Record how much baking soda it took to reach the desired pH level.