Name: _____________________________

Today’s Date: __________

Laboratory #35: Hollowing Out a Penny Objectives: To observe a redox reaction and learn about the reactivity of metals with acids. To correlate the results of the experiment with Table J On the Use of Acid: Wear protective clothing and goggles Add the acid to the water when diluting it, not the other way around In case of contact with skin, flush thoroughly with water. Neutralize with a weak solution of baking soda if necessary. Materials: Hydrochloric acid; Penny (mint date must be later than 1984); beaker or plastic cup; masking tape; goggles; gloves Procedure: (1) (2) (3) (4) (5) (6) (7) (8)

Obtain a piece of masking or laboratory tape and write your name on it. Obtain a small beaker or plastic cup and put the tape on the beaker. Obtain a penny minted after 1984 Using a triangular file, cut (file) several notches in the edge of the penny. Place the penny in a beaker. Add acid Observe the penny. Note any immediate changes, reactions, etc. Observe the penny some (>24 h.) later.

Data: Record your observations of the penny before submerging it in the acid, immediately after submersion and after extended submersion.

Conclusions & Questions: 1. Name the two metals that the penny of which the penny is composed.

2. Which metal in the penny reacted with the acid? Which metal did not?

3. What conclusions can you draw about the comparative reactivity of copper and zinc with acid? How does this compare to data on Table J?

4. Explain how to use Table J.

5. What is the formula for hydrochloric acid. What are the oxidation numbers?

6. What gas was formed during the reaction? Write the formula of the gas (recall that some gases are diatomic!). Is the gas listed on table J?

7. Was the hydrogen reduced or oxidized during the reaction? How do you know?

8. Write the word equation to describe the reaction between the penny and the acid.

9. What kind of chemical reaction occurred? (single replacement, double replacement, synthesis or decomposition) Explain your choice.

10. Write the formulae for the products and reactants in 7, above.

11. Write the balanced equation using the information from 9, above.

12. Write the half reactions for the oxidation and reduction.