Metals and acids
Which metal fizzes fastest?
Metals in acid
Strips of magnesium, aluminium, zinc and iron, and a copper piece, are each put into dilute hydrochloric acid in a lab.
What do you expect to see?
What this lesson covers
The idea
Metals react with dilute acids to give a salt and hydrogen, with reactivity decreasing in the order Mg > Al > Zn > Fe, while copper shows no reaction with dilute HCl.
Metals in acid
Strips of magnesium, aluminium, zinc and iron, and a copper piece, are each put into dilute hydrochloric acid in a lab.
What do you expect to see?
- Different amounts of bubbles
- The same bubbles in every tube
- No metal reacts
Five test tubes
Open every tab. The bubbles drawn show how fast the gas forms (a picture, not a count).
A pattern
Metal + dilute acid gives a salt and hydrogen. The bubbles are hydrogen gas. Magnesium gave the fastest bubbles and the most heat. The reactivity decreases in the order Mg > Al > Zn > Fe. Copper did not react with dilute HCl.
Metals react with dilute acids to give a salt and hydrogen, with reactivity decreasing in the order Mg > Al > Zn > Fe, while copper shows no reaction with dilute HCl.
Notes
Metal + dilute acid gives salt + hydrogen; reactivity falls in the order Mg > Al > Zn > Fe; copper does not react with dilute HCl.
Check yourself
Metal + dilute acid gives ...
Which of these metals reacts fastest with dilute HCl?
Which order of reactivity is correct?
What is seen when copper is put in dilute HCl?
- a salt and oxygen. The gas formed is hydrogen, not oxygen.
- a salt and hydrogen — correct. Yes!
- a metal oxide and water. A metal oxide forms when a metal combines with oxygen; with a dilute acid the products are a salt and hydrogen.
- Iron. Iron is the slowest of the four metals Mg, Al, Zn, Fe.
- Zinc. Zinc is slower than magnesium and aluminium.
- Magnesium — correct. Yes!
- Mg > Al > Zn > Fe — correct. Yes!
- Fe > Zn > Al > Mg. This is the reverse of the order in the book.
- Al > Mg > Fe > Zn. In the book, magnesium is the most reactive of these four and zinc is more reactive than iron.
- The fastest bubbles. The fastest bubbles were seen with magnesium.
- No bubbles and no change in temperature — correct. Yes!
- The most exothermic reaction. The most exothermic reaction was with magnesium; copper does not react with dilute HCl.