Question

Copper oxide is a/an while potassium hydroxide is a/an .

• A. base
• B. alkali
• C. acid
• D. salt

Answer 1

Answer: (A), (B)

The correct options are
A base
B alkali

A water soluble base is known as an alkali.
Copper oxide is a base because it will react with acids and neutralises them, but it is not an alkali because it does not dissolve in water. Potassium hydroxide is a base because it will react with acids and neutralises them. It's also an alkali because it dissolves in water.
Hence, all alkalis are bases but all bases are not alkalis.