Sodium: reactions of elements

Reaction of sodium with air

Sodium is easy to cut with a knife. The result is a shiny surface, but this soon dulls because of the action of air and moisture. If sodium is burnt in air the result is white sodium peroxide, Na2O2, together with some sodium oxide, Na2O, which is also white.

2Na(s) + O2(g) → 2Na2O2(s)

4Na(s) + O2(g) → 2Na2O(s)

Reaction of sodium with water

Sodium metal reacts rapidly with water to form a colourless solution of sodium hydroxide (NaOH) and hydrogen gas (H2). The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic. During the reaction, the sodium metal may well become so hot that it catches fire and burns with a characteristic orange colour. The reaction is slower than that of potassium (immediately below sodium in the periodic table), but faster than that of lithium (immediately above sodium in the periodic table).

2Na(s) + 2H2O → 2NaOH(aq) + H2(g)

Reaction of sodium with the halogens

Sodium metal reacts vigorously with all the halogens to form sodium halides. So, it reacts with fluorine, F2, chlorine, Cl2, bromine, I2, and iodine, I2, to form respectively sodium(I) bromide, NaF, sodium(I) chloride, NaCl, sodium(I) bromide, NaBr, and sodium(I) iodide, NaI.

2Na(s) + F2(g) → NaF(s)

2Na(s) + Cl2(g) → NaCl(s)

2Na(s) + Br2(g) → NaBr(s)

2Na(s) + I2(g) → NaI(s)

Reaction of sodium with acids

Sodium metal dissolves readily in dilute sulphuric acid to form solutions containing the aquated Na(I) ion together with hydrogen gas, H2.

2Na(s) + H2SO4(aq) → 2Na+(aq) + SO42-(aq) + H2(g)

Reaction of sodium with bases

Sodium metal reacts rapidly with water to form a colourless basic solution of sodium hydroxide (NaOH) and hydrogen gas (H2). The reaction continues even when the solution becomes basic. The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic. During the reaction, the sodium metal may well become so hot that it catches fire and burns with a characteristic orange colour. The reaction is slower than that of potassium (immediately below sodium in the periodic table), but faster than that of lithium (immediately above sodium in the periodic table). As the reaction continues, the concentration of hydroxide increases.

2Na(s) + 2H2O → 2NaOH(aq) + H2(g)

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