### ZIMSEC O Level Combined Science Notes: Experiment: The corrosion of metals by acids

Aim: Investigating the corrosion of some metals by acids

The corrosion of metals by acid gives off hydrogen gas

Materials: 5 test tubes, dilute hydrochloric acid, granulated zinc, iron fillings/iron nail, copper foil, aluminium foil, magnesium ribbon, splint burner.

Method

1. Place a small piece of each of the above metals into each one of the test tubes
2. Pour dilute hydrochloric acid into each test tube so that it just covers the metal
3. Observe each of the mixture for a few minutes
4. Place a thumb/cork over the mouth of one of the test tubs in which a gas is being produced in order to allow the gas to build up
5. When you feel pressure over your thumb/ it looks like much pressure has build up remove the thumb and quickly insert a lighted splint into the mouth of the test tube.

Observations and results

MetalRate of reactionLevel Corrosion
MagnesiumRapid evolution of bubbles and vigorous reactionQuickly disappears as it is corroded by the acid
ZincFast evolution of bubbles/rapid reactionIs quickly corroded
AluminumSlow evolution of bubblesIs corroded by the acid
IronThere is slow effervescenceThe metal is eaten away and corroded
CopperNone apparent /No reactionThe metal is not corrected at all
• Hydrogen gas is produced when the metals are corroded
• It burns with a pop sound when a lighted splint is inserted into test tube
• Copper does not react with the acid nor is it corroded

Conclusion

• Some metals are corroded by acid
• They react with hydrochloric acid to form a salt and hydrogen gas
• $\text{metal+acid}\rightarrow\text{salt+hydrogen}$
• Copper does not react with dilute hydrochloric acid

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