Many types of chemical reactions produce gaseous substances. These types of reactions may be classified as single displacement or double displacement reactions. In this experiment, you will investigate these types of reactions.

Materials
3M HCl
small pieces of zinc
small pieces of magnesium
Na₂CO₃
CaCO₃
spot plate
dropper

Procedure

1. Place a piece of Zn into a well and a piece of Mg into another. Place a small amount of the granular solids (the amount that would fit on the tip of a spatula) into the wells of the other spot plates as indicated on the diagram.
2. Add 10 drops of 3M HCl well and a piece of Mg into another. Place a small amount of the granular to each of the four wells.
3. Note any bubbling or fizzing action as the production of a gas.
4. Write a balanced equation for the reactions that occur. Include physical state symbols for the reactants and products.
5. There are two different gases produced in this set of reactions. What are the gases? What tests could you perform to verify your hypotheses?

Data and Observations

I. identity of gas produced ____________________________________

II. identity of gas produced ____________________________________

III. identity of gas produced ____________________________________

IV. identity of gas produced ____________________________________

V. identity of gas produced ____________________________________

What are the tests that will verify the identity of these gases?

Teacher's Notes

I. Zn (s) + 2HCl (aq) ---------> ZnCl₂ (aq) + H₂ (g)
II. Mg (s) + 2HCl (aq) ---------> MgCl₂ (aq) + H₂ (g)
III. Na2CO₃ (s) + 2HCl (aq) ----> 2NaCl (aq) + H₂O (l) + CO₂ (g)
IV. CaCO₃ (s) + 2HCl (aq) ---------> CaCl₂ (aq) + H₂O (l) + CO₂ (g)

Test for:

H₂(g): A burning splint will “pop” in the presence of hydrogen.
Hydrogen is explosive. Remember the Hindenberg? See Experiment 8.

CO₂(g): A burning splint will be extinguished in the presence of carbon dioxide. See Experiment 9.

Disposal

Aqueous solutions may be flushed down the sink with added water. Solids should be placed in a solid waste container.

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