# Reaction of potassium with water

In general, when we put potassium into water, it will produce potassium hydroxide and hydrogen:

$$\ce{2K + 2H2O ⟶2KOH + H2}$$

However isn't the following reaction also possible?

$$\ce{2K + H2O ⟶K2O + H2}$$

Why isn't the oxide produced?

• That's a chemical equation, not a formula (just nitpicking). Welcome to the site! People may say "$\ce{K2O}$ might be transiently formed", but it's too unstable to be isolated, especially in water. We might as well say that $\ce{KOH}$ is directly formed. Side note: A chemical equation can always be balanced, but that is no indication of whether the reaction is a fairy tale or not. Jun 5 '19 at 9:46
• Thanks for your answering. I am really appreciate your answer and manner. You even spot some mistakes in the question and let me have a good chance to learn. Thanks :) Jun 5 '19 at 11:10
• Thermodynamics comes into effect. Jun 6 '19 at 10:05

The reactions are ongoing this way:

Relatively free electrons of potassium reduce water:

$$\ce{2 e- + 2 H2O -> H2 + 2 OH-}\tag{1}$$

That leaves metal positively charged.

Liquid ammonia, if exposed to alkali metal, reacts with electrons much slower than water, forming a dark blue solution of solvated electrons. As electrons progressively kick out protons from ammonia, forming hydrogen, the solution finally turns to a colourless solution of NaNH2.

But back to water.

The potassium ions get hydrated, decreasing the charge.....

$$\ce{K(s)^{n+} -> K(s)^{(n-m)+} + m K+} \tag{2}$$

forming $$\ce{KOH}$$ solution in form of mixture of hydrated ions $$\ce{K+ + OH-}$$

But heavy potassium ions cannot keep pace with light and fast electrons and the drop of melted metal progressively gains positive charge and finally ends up by - as authors call it - Coulombic explosion.

The hydrogen gets eventually ignited by microsparcs due the charge instability even before the explosion. As "Terminator T1000-like" spikes of liquid metal eventually pierce isolating vapour+hydrogen layer, getting into contact with ignitable hydrogen-air mixture.

It was recently theoretically predicted by quantum chemistry simulation for several dozens of alkali atoms by Czech chemist Pavel Jungwirth And col. Chemistryworld-Alkali metal explosion explained

They have experimentally verified it by high speed 10000 f/s camera, using sodium/potassium alloy forming an eutectic with low melting point.

I knew that from the popular science radio broadcast interview, finding backwards some reference for it.