Question

Alkali metal (M, group $1$) react with water to form an aqueous alkali metal hydroxide $\left(MOH\right)$ and hydrogen gas as shown by the general equation below:

$2M\left(s\right)+2H_{2}O\to 2MOH\left(aq\right)+H_2\left(g\right)$

Which element would react most rapidly with water?

• A. Lithium $\left(Li\right)$
• B. Sodium $\left(Na\right)$
• C. Potassium $\left(K\right)$
• D. Rubidium $\left(Rb\right)$

Answer 1

The correct option is C Potassium $\left(K\right)$

Lithium sodium and potassium all react vigorously with water. Alkali metals need to be stored under oil to prevent them reacting with the oxygen and water vapor in the air. The reactivity of the alkali metals increases down the group. Potassium reacts more vigorously than sodium and lithium is the least reactive.