Potassium and sodium are both highly reactive metals, so their elementary substance do not exist in nature; they usually form compounds with other elements. Their properties are determined by the negatively charged part of the compound, so compounds of sodium and potassium have similar characteristics. Let's focus on sodium compounds below.
Sodium Oxide
It is a white powder that needs to be stored in a sealed container, as it reacts with carbon dioxide and water in the air.
1. Sodium oxide can react with water to form sodium hydroxide.
Na₂O(s) + H₂O(l) = 2NaOH(aq)
2. Sodium oxide can react with acids to produce the corresponding sodium salts and water. If there is an excess of sodium oxide, it will continue to react with water to form sodium hydroxide.
Na₂O(s) + 2H⁺(aq) = 2Na⁺(s) + H₂O(l)
3. Sodium oxide can react with acidic oxides.
Na₂O(s) + CO₂(g) = Na₂CO₃(s)
Na₂O(s) + SO₂(g) = Na₂SO₃(s)
4. Sodium oxide can be oxidized to sodium peroxide when heated.
2Na₂O(s) + O₂(g) = 2Na₂O₂(s)
Sodium Peroxide:
It is a yellow powder that needs to be stored in a sealed container, as it reacts with carbon dioxide and water in the air.
1. Sodium peroxide reacts with water to form sodium hydroxide and hydrogen peroxide. Hydrogen peroxide is a strong oxidizing agent, so sodium peroxide is also used for bleaching objects.
Na₂O₂(s) + 2H₂O (g) = 2NaOH(aq) + H₂O₂(aq)
2. Sodium peroxide reacts with carbon dioxide to produce sodium carbonate and oxygen. This property allows it to absorb carbon dioxide and produce oxygen in gas masks and submarines.
2Na₂O₂(s) + 2CO₂(g) = 2Na₂CO₃(s) + O₂(g)
Sodium Salts
Table salt, also known as sodium chloride, is an ionic compound with the chemical formula NaCl. It is commonly used as a condiment and food preservative. Table salt plays an important role in maintaining osmotic pressure and nerve electrical impulses in the body. Sodium hydroxide is produced from the electrolysis of an aqueous solution of sodium chloride. Hydrogen and chlorine are by-products of this process.
2NaCl(aq) + 2H₂O(l) = 2NaOH(aq) + H₂(g) + Cl₂(g)
Sodium Carbonate, also known as soda. It is a white solid that is easily soluble in water. The aqueous solution is alkaline and is difficult to decompose when heated. Sodium carbonate can react with acids to release carbon dioxide.
Na₂CO₃(aq) + 2HCl(aq) = 2NaCl(aq) + H₂O(l) + CO₂(g)
Sodium Bicarbonate, also known as baking soda. It is a white solid that is easily soluble in water. The aqueous solution is alkaline and decomposes when heated. Sodium bicarbonate can react with acids to release carbon dioxide, and this reaction is more vigorous.
NaHCO₃(aq) + HCl(aq) = NaCl(aq) + H₂O(l) + CO₂(g)
Sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. Sodium hydroxide is a highly corrosive alkali that decomposes lipids and proteins at room temperatures and may cause severe chemical burns. It is highly soluble in water, and readily absorbs moisture and carbon dioxide from the air.
It reacts with carbon dioxide. When there is insufficient carbon dioxide, the product is sodium carbonate; when there is abundant carbon dioxide, the product is sodium bicarbonate. It can also react with silicon dioxide (one of the main components of glass) to produce sodium silicate. Sodium silicate is an adhesive, so glass bottles containing sodium hydroxide cannot be sealed with glass stoppers, but with cork stoppers.
2NaOH(aq) + CO₂(g) → Na₂CO₃(aq) + H₂O(l)
NaOH(aq) + CO₂(g) → NaHCO₃(aq)
2NaOH(aq) + SiO₂(s) → Na₂SiO₃(aq) + H₂O(l)