Batteries produce explosive blank gas when being charged.

• A. Hydrogen
• B. Oxygen
• C. Nitrogen
• D. Chlorine

Answer: (A)

When a battery with an aqueous electrolyte is charged, the electrolyte undergoes electrolysis, splitting water into hydrogen and oxygen. The hydrogen gas forms at the negative plate and tends to vent from the cell. Hydrogen is highly flammable and forms explosive mixtures with air over a wide range of concentrations, so if it accumulates in a confined space and meets a spark or flame, it can explode. The other gases listed aren’t the explosive product produced in this charging process for typical batteries (oxygen is produced but isn’t explosive on its own; nitrogen and chlorine aren’t generated in standard charging reactions). Therefore, the gas is hydrogen.