What is sodium bicarbonate?

Introduction

Sodium bicarbonate (NaHCO?) (Sodium Bicarbonate), commonly known as baking soda. White fine crystals, less soluble in water than sodium carbonate. It is also an industrial chemical. The solid begins to decompose gradually above 50℃ to form sodium carbonate, carbon dioxide and water, and completely decomposes at 270℃. Sodium bicarbonate is an acid salt formed after the neutralization of a strong base and a weak acid. It is weakly alkaline when dissolved in water. This property allows it to be used as a leavening agent in food preparation. After sodium bicarbonate is used, sodium carbonate will remain. If used too much, the finished product will have an alkaline smell.

Physical properties

Sodium bicarbonate is white crystal, or opaque monoclinic fine crystal. Specific gravity 2.15. Odorless, non-toxic, salty in taste, soluble in water and slightly soluble in ethanol. It is soluble in 10 parts of water at 25℃ and 12 parts of water at about 18℃. Its aqueous solution is slightly alkaline due to hydrolysis. It is stable at room temperature and easily decomposes when heated. It gradually decomposes above 50°C and completely loses carbon dioxide at 270°C. It has no change in dry air and slowly decomposes in humid air.

Chemical properties

Easily decomposes when heated. Decomposes slowly in moist air. The reaction starts to produce CO? at about 50°C, and all turns into sodium carbonate at 100°C. It decomposes rapidly in weak acid. Its aqueous solution begins to decompose into carbon dioxide and sodium carbonate at 20°C, and completely decomposes at the boiling point. The unstirred solution made of cold water only shows a slightly alkaline reaction to the phenolphthalein test paper. When placed or the temperature is raised, its alkalinity increases. The pH value of a freshly prepared 0.1mol/L aqueous solution at 25°C is 8.3. Low toxicity, LD50 (rat, oral) 4420mg/kg.

Reaction with acid:

Reaction with HCl: NaHCO?+HCl ——→NaCl+H?O+CO?↑

Reaction with CH?COOH ：NaHCO?+CH?COOH——→CH?COONa+H?O+CO?↑

Reaction with alkali:

Reaction with sodium hydroxide: NaHCO?+NaOH— —→ Na?CO?+ H?O

Reaction with calcium hydroxide: The dosage of sodium bicarbonate should be divided into excessive and small amounts.

A small amount: NaHCO?+ Ca(OH)?——→ CaCO?↓+ NaOH + H?O

Excess: 2NaHCO?+ Ca(OH)?——→ Na ?CO?+ CaCO?↓+ 2H?O

Reaction with salt:

Reaction with copper sulfate: 4NaHCO?+2CuSO?——→2Na?SO?+Cu?( OH)?CO?↓+H?O+3CO?↑

Hydrolysis:

Double hydrolysis with aluminum chloride: 3NaHCO?+ AlCl?——→Al(OH)? ↓+ 3CO?↑+ 3NaCl