What oxidizing chemical consists of 2 parts hydrogen and 2 parts oxygen?

Hydrogen peroxide is the correct answer because it has the chemical formula H₂O₂, which indicates that it consists of two parts hydrogen (H) and two parts oxygen (O). This compound is widely used as an oxidizing agent in various hair coloring and lightening products due to its ability to release oxygen when it decomposes, thereby lifting color from the hair. In cosmetic chemistry, the oxidizing properties of hydrogen peroxide are essential for the oxidation reactions involved in hair dyeing processes.

Ammonia, on the other hand, is a compound with the formula NH₃, consisting of nitrogen and hydrogen, and does not contain oxygen at all. Hydrochloric acid is represented by HCl, indicating one hydrogen and one chlorine atom, with no oxygen, making it unsuitable as an oxidizing agent in this context. Bleach typically refers to sodium hypochlorite or hydrogen peroxide in various formulations, but referring specifically to bleach does not allow for the clear identification of its chemical composition as it can contain multiple chemicals, and is not characterized by the precise ratio of hydrogen and oxygen in the way hydrogen peroxide is. Thus, hydrogen peroxide uniquely fits the criteria specified in the question.