Ways to Make Hydrochloric Acid
Hydrochloric acid (HCl) can be produced primarily through two chemical methods: the direct reaction of hydrogen and chlorine gases, and the reaction of concentrated sulfuric acid with solid sodium chloride. Each method has specific conditions and safety concerns that determine its practicality.
1. Reaction of Hydrogen and Chlorine
The direct combination of hydrogen (H2) and chlorine (Cl2) gases produces hydrochloric acid gas:
H2 + Cl2 → 2HCl
This reaction is highly explosive and hazardous. Exposure to bright light can trigger a violent explosion, making it unsuitable for most settings outside of specialized industrial environments.
Industrially, a controlled process involves passing a mixture of hydrogen and chlorine gases through a heated tube made from HCl-resistant metal at around 800°C. The resulting HCl gas is then cooled and dissolved in water to obtain hydrochloric acid. This method requires careful temperature control and safety measures.
2. Dripping Concentrated Sulfuric Acid onto Solid Sodium Chloride (Preferred Lab Method)
A safer and more practical method for producing HCl gas at smaller scales involves the reaction of concentrated sulfuric acid (H2SO4) with sodium chloride (NaCl):
NaCl (s) + H2SO4 (conc) → HCl (g) + NaHSO4 (s)
In this reaction, HCl gas is released and must be carefully collected by conducting it through a delivery tube over water. The gas dissolves in water, forming hydrochloric acid solution.
- A key operational step is avoiding immersing the tube end in water. Doing so causes rapid dissolution and suction of water back into the reaction flask, which can lead to dangerous consequences.
- The tube height is gradually adjusted as the water level rises during absorption, until no more gas produces HCl in solution.
3. Commercial Availability
Hydrochloric acid is widely available via chemical suppliers worldwide. Purchasing concentrated hydrochloric acid is typically safer and more cost-effective than making it in non-industrial settings.
For example, a brand called AERO offers a 91% pure hydrochloric acid concentrate, which is near the maximum stable concentration. This product remains liquid over a temperature range from about 13°F to 220°F, highlighting its stability.
AERO hydrochloric acid is accessible in certain US states such as Kentucky, Tennessee, and West Virginia, often corresponding to chemical supply availability in those regions.
Key Takeaways
- Direct reaction of hydrogen and chlorine produces HCl but is dangerously explosive and mainly industrial.
- Dripping concentrated sulfuric acid on sodium chloride releases HCl gas, which dissolves in water to form hydrochloric acid; caution is necessary to avoid backflow.
- Hydrochloric acid is commercially purchasable, often safer and more convenient than producing it in a home laboratory.
- AERO hydrochloric acid represents a highly pure, stable commercial concentrate with specific temperature stability.
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