Question

Balance `"K + H"_2"O" -> "KOH" +"H"_2` ?

Answer 1

Balanced equation

`"2K(s) + 2H"_2"O("l")"` `rarr` `"2KOH(aq) + H"_2("g")"`

Explanation:

Alkali metals react vigorously with water to form the metal hydroxide and hydrogen gas.

Balanced equation

`"2K(s) + 2H"_2"O("l")"` `rarr` `"2KOH(aq) + H"_2("g")"`

This is a very dangerous reaction. Since water is pretty much everywhere, including water vapor in the air and in the sweat of your skin, alkali metals are stored in kerosene or mineral oil.

Answer 2

Well, this is formally a redox reaction....

Explanation:

Potassium metal, a potent reducing agent, is oxidized to potassium ion....

`K(s) rarr K^+ + e^(-)`

And hydrogen ion in water is reduced to dihydrogen gas....

`H_2O(l) + e^(-)rarrHO^(-) + 1/2H_2(g)uarr`

And as always we add the half-equations together such that the electrons are eliminated as particles of convenience....

`K(s) + H_2O(l) rarr underbrace(K^(+)""^(-)OH)_"potassium hydroxide(aq)"+1/2H_2(g)uarr`