Which of the following solutions is most basic?

What happens when metal oxide reacts with water?

Who defined acid and base on the basis of chemical properties?

$Na_{2}CO_{3} \cdot 10H_{2}O$ and $Na_{2}CO_{3}$ are two chemical compounds. Write their chemical names. Explain the significance of $10H_{2}O$ and mention the term used for water molecules attached to a salt.

According to the Arrhenius theory,which ion is produced when a base ionizes in water?

Write the chemical names of two salts belonging to the sodium family.