Question

What is produced when potassium reacts with water?
$2{{K}_{(s)}}+2{{H}_{2}}O\xrightarrow{{}}?$

Answer 1

Hint: We know that reaction is exothermic, that is energy is released during the reaction, also the resultant solution from the reaction is highly alkaline because of the presence of hydroxide ion, coming from the strong base Potassium hydroxide. This reaction proceeds with a lot of spits and sparks.

Complete answer:
Potassium metal reacts very rapidly with water to form a colorless solution of potassium hydroxide \[\left( KOH \right)\] and hydrogen gas \[\left( {{H}_{2}} \right).\] Hydrogen evolved during the reaction ignites rapidly. The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic. Early in the reaction, the potassium metal becomes so hot that it catches fire and burns with a characteristic plate lilac colour. The reaction is slower than that of rubidium (immediately below potassium in the periodic table), but faster than that of sodium (immediately above potassium in the periodic table).
Potassium is an alkali metal. It is much more reactive than sodium, whose reactions you may have seen.
We can represent its reaction with water by following equation :\[{{K}_{\left( s \right)}}+{{H}_{2}}{{O}_{\left( l \right)}}\to KO{{H}_{\left( aq \right)}}+\dfrac{1}{2}{{H}_{2\left( g \right)}}\]
All the alkali metals react vigorously with cold water. In each reaction, hydrogen gas is given off and the metal hydroxide is produced. The speed and violence of the reaction increases as you go down the metal hydroxide that produces the group. This shows that the reactivity of the alkali metals increases as you go down Group one.

Note:
Remember that potassium hydroxide \[\left( KOH \right)\] is an inorganic compound and is commonly known as caustic potash. It is a strong base. Potassium hydroxide is usually translucent pellets which becomes tacky on contact with air, because $KOH$ is hygroscopic.