Final answer:
The acid used in automobile batteries is sulfuric acid, which serves as a vital electrolyte for the chemical reactions within the battery. Modern batteries are sealed to prevent acid leakage and protect users from the hazards associated with handling sulfuric acid option(4).
Step-by-step explanation:
The acid used in automobile batteries is sulfuric acid. Automobile batteries, also known as lead-acid batteries, rely on sulfuric acid as a key component to function. Within a car battery, sulfuric acid acts as a strong electrolyte that ionizes into hydrogen ions and sulfate ions, which are vital for the battery's electrochemical reactions.
Sulfuric acid also has a broad range of uses beyond automobile batteries, including domestic acidic drain cleaners and as an industrial chemical. Older car batteries had openings that allowed for sulfuric acid levels to be replenished. However, due to the potential hazards of handling sulfuric acid, modern batteries are now sealed.
This development prevents the acid from leaking and protects users from potential acid burns. Hence, sulfuric acid's crucial role in generating electricity within the battery and its hazardous nature make its proper management essential.