Making & Testing CO2
Problem:
We will attempt to make CO2 from calcium carbonate and hydrochloric acid. We will then test the purity of our work using three different methods
1. Phenol red
2. Match test
3. calcium hydroxide
Materials:
1. calcium hydroxide (CaCO3)(to make lime water)
2. phenol red
3. 3 molar hydrochloric acid (HCl)
4. 10g marble chips
5. water trough
6. hose
7. gas generating bottle
(see diagram)
8. 3 25ml flasks
9. 400ml beaker
10. 2 test tubes
11. filter paper
12. rags and paper towels
Safety:
1. Wear apron and safety glasses at all times during the experiment
2. Hydrochloric acid will be poured at teachers desk in front of teacher only. NO EXCEPTIONS
Procedure:
1. fill water trough most of the way with water
2. put 10g CaCO3 in gas generating bottle
3. put acid (30ml) in thistle tube funnel
4. add HCl to thistle tube, covering the bottom of the glass tube in the bottle thoroughly
5. wait approximately 30seconds to one minute for the trapped air to run through the thistle tube
6. fill 3 25 ml bottles (completely) with water and turn upside down in water trough (keeping your thumb over the opening of the bottle to keep from losing any water from the bottle
7. hold the bottles one at a time over the bubble opening in the trough. As CO2 fills the bottle, it will completely replace the water
8. when bottles are completely filled with CO2 hold thumb over 25ml bottle opening and place on desk (upside down)
9. rinse bottle and water trough in sink immediately and put away
10. use rags to clean and dry work table surface. Use paper towels to dry off marble chips
Chemical Reaction:
calcium carbonate + hydrochloric acid -----> calcium chloride + carbon dioxide + water
CaCO3 + HCl -----> CaCl2 + CO2 + H2O
Three Tests for CO2 Purity
1. Phenol red test: pour alittle phenol red in the bottom of one of the phenol red flasks. The contents of the flask should turn yellow
2. Match test: put lit match up to opening of one of the CO2 flasks
What happens?
a. H2--
b. O2--
c. CO2--
3. Calcium Hydroxide: put alittle in a test tube (using a spatula), about half full with water. Shake, and pour into a clean test tube using funnel paper. This will produce pure lime water
Pour CO2 into the test tube with lime water. This should produce a milky white precipitate
Ca(OH)2 + CO2 -------> CaCO3 + H2O
(lime water)
Conclusion:
1. What test is used to determine if an unknown gas is hydrogen?
2. What test is used to determine if an unknown gas is oxygen?
3. What test is used to determine if an unknown gas is carbon dioxide?