Which of the following is produced when acid reacts with metals? 

The correct answer is Salt and hydrogen gas.

Key Points

• When acids react with metals, they produce a salt and hydrogen gas.
• This is a typical single displacement reaction where the metal displaces hydrogen from the acid.
• For example, when zinc (Zn) reacts with hydrochloric acid (HCl), it forms zinc chloride (ZnCl₂) and hydrogen gas (H₂).
• The general equation for this type of reaction is: Metal + Acid → Salt + Hydrogen gas.
• Common metals that react with acids include zinc, magnesium, and iron.

Additional Information

• Oxidation-Reduction Reaction: In the reaction between acids and metals, the metal undergoes oxidation (loses electrons) and hydrogen ions (H⁺) from the acid are reduced (gain electrons).
• Reactivity Series: Not all metals react with acids. The reactivity series of metals determines which metals will react with acids to produce hydrogen gas.
• Safety Precautions: The reaction between metals and acids can be vigorous and produce hydrogen gas, which is highly flammable. Proper safety measures should be taken.
• Applications: This type of reaction is utilized in various industrial processes including the production of hydrogen gas and in metal refining.