What compound is formed when a small amount of hydrochloric acid is added to a beaker containing copper oxide? 

The correct answer is Copper (II) chloride.

Key Points

• When hydrochloric acid (HCl) is added to copper oxide (CuO), a reaction occurs producing copper (II) chloride (CuCl₂) and water (H₂O).
• The balanced chemical equation for this reaction is: CuO + 2HCl → CuCl₂ + H₂O.
• This reaction is an example of a neutralization reaction where an acid reacts with a base (metal oxide) to produce a salt and water.
• Copper (II) chloride is a compound with copper in the +2 oxidation state, which is the most stable oxidation state for copper in aqueous solutions.

Additional Information

• Hydrochloric Acid (HCl)
  • Hydrochloric acid is a strong, corrosive acid commonly used in laboratory and industrial applications.
  • It is a solution of hydrogen chloride in water and is known for its pungent smell.
  • HCl is widely used for cleaning metals, in the production of organic compounds, and in the food industry for processing and cleaning.
• Copper Oxide (CuO)
  • Copper oxide is a black solid that is used as a pigment in ceramics and glass.
  • It is a basic oxide, meaning it reacts with acids to form salts and water.
  • CuO is also used in the production of copper salts and as a catalyst in chemical reactions.
• Copper (II) Chloride (CuCl₂)
  • Copper (II) chloride is a yellow-brown solid that dissolves in water to form a blue-green solution.
  • It is used in dyeing, printing, and in various chemical syntheses.
  • CuCl₂ can also act as a catalyst in organic reactions and is used in water treatment processes.
• Neutralization Reaction
  • A neutralization reaction is a chemical reaction in which an acid and a base react to form a salt and water.
  • This type of reaction typically results in the neutralization of the pH of the reacting solutions.
  • Neutralization reactions are fundamental in various industrial processes and in everyday life, such as in antacid tablets used to relieve heartburn.