Bases and metals
Some metals react with a base, but not all.
Zinc meets a base
Zinc made hydrogen when we put it in an acid. Now a teacher puts zinc in a base: sodium hydroxide solution.
What do you think happens?
What this lesson covers
The idea
A base reacts with some metals to give hydrogen gas and a salt whose negative ion is composed of the metal and oxygen; such reactions are not possible with all metals.
Zinc meets a base
Zinc made hydrogen when we put it in an acid. Now a teacher puts zinc in a base: sodium hydroxide solution.
What do you think happens?
- Hydrogen gas bubbles out again
- Nothing: a base never touches a metal
- Oxygen gas bubbles out
Four metals, one base
A teacher drops each metal into sodium hydroxide solution and warms it gently. Try all four.
Zinc made a salt called sodium zincate. Look at its ions.
Some metals, not all
A base reacts with some metals to give hydrogen gas and a salt whose negative ion is made of the metal and oxygen. Such reactions are not possible with all metals.
2NaOH(aq) + Zn(s) → Na₂ZnO₂(s) + H₂(g)
- Zn + HCl | Zn + NaOH
- Gas | H₂ | H₂
- Salt | ZnCl₂ | Na₂ZnO₂ (sodium zincate)
- Negative ion | Cl⁻ | ZnO₂²⁻ (zinc + oxygen)
Notes
A base reacts with some metals to give hydrogen gas and a salt whose negative ion is composed of the metal and oxygen; such reactions are not possible with all metals.
Check yourself
Zinc reacts with sodium hydroxide. Which gas is formed?
Copper granules are warmed with sodium hydroxide solution. What do you see?
In sodium zincate, Na₂ZnO₂, the negative ion is …
Which statement is right?
- Oxygen. The gas is hydrogen, the same as with an acid.
- Hydrogen — correct. Yes! Zinc + base also gives hydrogen gas.
- Carbon dioxide. There is no carbon here, so no carbon dioxide.
- Hydrogen bubbles. Only some metals, like zinc, give hydrogen with a base. Copper does not.
- The copper dissolves with a fizz. Copper does not react with sodium hydroxide solution.
- No bubbles: nothing happens — correct. Yes! Copper does not react with the base.
- ZnO₂²⁻ (zinc and oxygen together) — correct. Yes! The metal is inside the negative ion.
- Zn²⁺. Here the zinc is part of the negative ion, together with oxygen.
- Na⁺. Na⁺ is the positive ion.
- A base reacts with every metal. Copper, magnesium and iron do not react with it.
- A base reacts with some metals, not with all — correct. Yes!
- A base never reacts with any metal. Zinc does react with a base.