International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What is a common application of hydrogen chloride?

1. Explosive manufacturing

2. Water treatment

3. Soap production

4. Conducting electricity

The correct answer is: Water treatment

Hydrogen chloride is commonly used in water treatment processes. It is often involved in the neutralization of alkaline water to help adjust the pH level, ensuring that the water is safe for consumption and adheres to regulatory standards. This strong acid can effectively reduce the pH of water that has become too basic, thereby facilitating the removal of impurities and improving the overall quality of the water. In context, the other applications mentioned are not typical uses for hydrogen chloride. While explosive manufacturing may involve other specific chemicals, hydrogen chloride’s role is not aligned with producing explosives. Similarly, soap production primarily relies on alkalis and fats, not hydrogen chloride. Conducting electricity is associated with electrolytes and ionic solutions, whereas hydrogen chloride in its gaseous form does not conduct electricity; it needs to be in solution for any ionic conduction to occur. Therefore, the application of hydrogen chloride in water treatment clearly stands out as the most appropriate choice.