When a nickel cadmium battery is overcharging, which gases are produced?

When a nickel cadmium (NiCad) battery is overcharging, it undergoes a process called gassing. This occurs as a result of electrolysis of the electrolyte, leading to the production of gases. In the case of overcharging, both oxygen and hydrogen gases are generated.

The process specifically involves the electrolyte breaking down at high voltages, which leads to the formation of oxygen at the positive plate and hydrogen at the negative plate. It's important to note that during overcharging, the amount of hydrogen produced can be significant enough to create an explosive mixture when combined with oxygen in the presence of a spark or flame. This makes the generation of oxygen and explosive hydrogen a critical safety consideration when managing overcharging scenarios with nickel cadmium batteries.

In comparison, the other choices do not accurately represent the chemistry involved during the overcharging of nickel cadmium batteries. Carbon dioxide and nitrogen, as well as hydrogen and helium, are not produced in this specific context. Thus, the generation of oxygen and explosive hydrogen is the correct and relevant outcome when a nickel cadmium battery is overcharged.