Oxides that dissolve
Some metal oxides form alkalis.
Into the water
Most metal oxides do not dissolve in water. A few do.
What do the oxides of sodium and potassium form in water?
What this lesson covers
The idea
Most metal oxides are insoluble in water, but some, like sodium oxide and potassium oxide, dissolve in water to form alkalis.
Into the water
Most metal oxides do not dissolve in water. A few do.
What do the oxides of sodium and potassium form in water?
- An alkali
- A pure metal
- An acid
Insoluble or soluble
Open every tab.
A few dissolve
Most metal oxides are insoluble in water. But sodium oxide and potassium oxide dissolve in water, and the solution is an alkali: sodium hydroxide or potassium hydroxide.
Most metal oxides are insoluble in water, but some, like sodium oxide and potassium oxide, dissolve in water to form alkalis.
Notes
Most metal oxides are insoluble, but sodium oxide and potassium oxide dissolve in water to form alkalis.
Check yourself
Most metal oxides are ... in water.
Sodium oxide dissolves in water to form ...
Potassium oxide with water gives ...
In Na₂O + H₂O gives 2NaOH, how many sodium atoms are in 2NaOH?
Answer: 2
2 × NaOH has 2 × 1 = 2 sodium atoms, the same as the 2 in Na₂O.
- insoluble — correct. Yes!
- soluble. Only some, like sodium oxide and potassium oxide, are soluble.
- very soluble. Only some metal oxides, like sodium oxide and potassium oxide, dissolve in water.
- sodium chloride. No chlorine is involved: Na₂O + H₂O gives NaOH.
- sodium hydroxide, an alkali — correct. Yes!
- hydrochloric acid. The solution is an alkali, not an acid.
- potassium metal. Metal oxide plus water gives KOH, not the metal.
- potassium sulphate. No sulphur is involved: K₂O + H₂O gives KOH.
- potassium hydroxide — correct. Yes!