Question

which of these gases is produced by a battery during charging?
a. helium
b. argon
c. nitrogen
d. hydrogen
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Explanation:

When a battery (such as a lead - acid battery) is charging, water ($H_2O$) in the electrolyte can undergo electrolysis. The chemical reaction for the electrolysis of water is $2H_2O
ightarrow2H_2 + O_2$. Helium ($He$), argon ($Ar$), and nitrogen ($N_2$) are not involved in the typical charging reactions of common batteries. Hydrogen ($H_2$) is one of the gases produced during the charging process (the other is oxygen, but it is not among the options here).

Answer:

D. Hydrogen