Reaction with water
When a small piece of potassium is added to water, it produces a hissing sound as it burns with
a lilac flame. It also moves about quickly on
the water surface. [image]
Hydrogen gas is given out in the reaction. The resulting alkaline solution will
turn red litmus blue because of the potassium hydroxide formed.
potassium + water —> potassium hydroxide solution + hydrogen
4K(s) + 4H2O(l) —> 4KOH (aq) + 2H2(g)
Reaction with oxygen
Potassium burns vigorously in oxygen, so only gentle heating
is required to make it burn. It gives a lilac flame to produce
an orange powder.
Potassium + oxygen —> potassium superoxide
K(s) + O2(g) —> KO2(s)
Reaction with dilute acids
Potassium reacts with dilute acids explosively. DO NOT attempt these experiments in the school laboratory.
Potassium reacts with dilute hydrochloric acid to give potassium chloride and hydrogen gas.
potassium + dilute hydrochloric acid —> potassium chloride + hydrogen
2K(s) + 2HCl(aq) —> 2KCl(aq) + H2(g)
Potassium reacts with dilute sulphuric acid to give potassium sulphate and hydrogen gas.
potassium + dilute sulphuric acid —> potassium sulphate + hydrogen
2K(s) + H2SO4 (aq) —> K2SO4(aq) + H2(g)
Potassium reacts with dilute nitric acid to give potassium nitrate and hydrogen gas.
potassium + dilute nitric acid —> potassium nitrate + hydrogen
2K(s) + 2HNO3(aq) —> 2KNO3(aq) + H2(g)