Gas tests
Aim: You will be combining the following substances and testing the gas produced to identify it as
either: O2, H2 or CO2. You may be able to identify the gas produced just be looking at the chemical
formulas of the elements and compounds involved in the reaction. You need to put some drops of
universal indicator into the solution to see if it is acid, neutral or alkali and this should make the
identity of the liquid compound obvious.
Equipment: For each experiment you will need the following equipment:
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Boiling tube and bung
Splint
Matches
Universal indicator
Procedure: For each reaction you will need to combine the reactants and then test for the gas using
a lit splint. Once you have identified the gas see if you can work out the other compounds from the
remaining elements.
Magnesium and hydrochloric acid:
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Observations _______________________________________________________________________________
Magnesium + Hydrochloric Acid  Magnesuim Chloride + __________
Can you write the chemical equation?
Mg + HCl  _______+____
Potato and hydrogen peroxide:
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Observations _______________________________________________________________________________
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Potato is a catalyst, which means that it doesn’t change in the reaction.
Potato + Hydrogen peroxide  Potato+ Water + _________
Potato + H2O2  Potato + ____ + ____
Calcium carbonate and hydrochloric acid:
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Observations _______________________________________________________________________________
Calcium carbonate + hydrochloric acid → calcium chloride + water + ___________
CaCO3 + 2HCl  CaCl + _____ + _____
Observations
Discussion
1. Which test do you believe tested for the presence of oxygen? Explain why based
on your observations of the splint. Name 1 use of this gas in every day life.
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2. Which test do you believe tested for the presence of carbon dioxide? Explain why
based on your observations of the splint. Name 1 use of this gas in everyday life.
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3. Which test do you believe tested for the presence of hydrogen? Explain why
based on your observations of the splint. Name 1 use of this gas in everyday life.
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Gas
Test
Result if gas present