Chemical Properties of Sodium
Sodium is a very reactive substance. It decomposes water energetically, liberating hydrogen and forming sodium hydroxide, the reaction with ice beginning at -98° C.
2Na+2H2O = 2NaOH+H2.
Normally, the heat of the reaction is insufficient to ignite the hydrogen, but if the water is at a temperature of 60° C., or if the free motion of the sodium is impeded by placing it on filter-paper or by increasing the viscosity of the water by addition of gum-arabic, the evolved hydrogen ignites and burns with a characteristic yellow flame.
Ozone reacts with a solution of sodium in liquid ammonia, yielding an orange to brown precipitate. The product is readily decomposed by water or dilute acids with evolution of oxygen. It is possibly an ozonide of sodium, but owing to interaction of the ozone and ammonia it has not been found possible to isolate it in the pure state. Potassium, rubidium, and caesium react similarly.
Moisture plays an important part in promoting the interaction of sodium and other substances. When quite dry, the halogens, oxygen, and hydrogen chloride do not combine with the metal, or react very slowly; but in presence of a trace of moisture these substances react vigorously with sodium, forming respectively the halide, oxide, and chloride.
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