Potassium behaves rather like sodium except that the reaction is faster and enough heat is given off to set light to the hydrogen. The colour is due to contamination of the normally blue hydrogen flame with sodium compounds. If the sodium becomes trapped on the side of the container, the hydrogen may catch fire to burn with an orange flame. The sodium moves because it is pushed around by the hydrogen which is given off during the reaction. A white trail of sodium hydroxide is seen in the water under the sodium, but this soon dissolves to give a colourless solution of sodium hydroxide. Sodium also floats on the surface, but enough heat is given off to melt the sodium (sodium has a lower melting point than lithium and the reaction produces heat faster) and it melts almost at once to form a small silvery ball that dashes around the surface. The reaction generates heat too slowly and lithium's melting point is too high for it to melt (see sodium below). It gradually reacts and disappears, forming a colourless solution of lithium hydroxide.
Lithium's density is only about half that of water so it floats on the surface, gently fizzing and giving off hydrogen. In each of the following descriptions, I am assuming a very small bit of the metal is dropped into water in a fairly large container. This equation applies to any of these metals and water - just replace the X by the symbol you want. In each case, a solution of the metal hydroxide is produced together with hydrogen gas. It uses these reactions to explore the trend in reactivity in Group 1.Īll of these metals react vigorously or even explosively with cold water. This page looks at the reactions of the Group 1 elements - lithium, sodium, potassium, rubidium and caesium - with water.
REACTIONS OF THE GROUP 1 ELEMENTS WITH WATER
Reactions of the Group 1 elements with water
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