Question Video: Definition of Photochemical Reactions Chemistry

Which of the following statements correctly describes a photochemical reaction? [A] A photochemical reaction is a chemical reaction that occurs without the absorption of energy from light. [B] A photochemical reaction is a chemical reaction that releases bright flashes of light. [C] A photochemical reaction is a chemical reaction initiated by an increase in temperature. [D] A photochemical reaction is a chemical reaction that does not involve the transfer of electrons. [E] A photochemical reaction is a chemical reaction initiated by the absorption of energy from light.

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Video Transcript

Which of the following statements correctly describes a photochemical reaction? (A) A photochemical reaction is a chemical reaction that occurs without the absorption of energy from light. (B) A photochemical reaction is a chemical reaction that releases bright flashes of light. (C) A photochemical reaction is a chemical reaction initiated by an increase in temperature. (D) A photochemical reaction is a chemical reaction that does not involve the transfer of electrons. (E) A photochemical reaction is a chemical reaction initiated by the absorption of energy from light.

A photochemical reaction is a reaction that’s initiated by absorbing light. We can identify these kinds of reactions because light will appear above the reaction arrow in the chemical equation. This definition clearly seems to match answer choice (E), but let’s take a quick look through our other answer choices.

Answer choice (A) says that a photochemical reaction occurs without the absorption of energy from light, which is clearly the opposite of what a photochemical reaction is. So, this isn’t correct. Our next answer choice says that a photochemical reaction releases bright flashes of light. There are plenty of examples of chemical reactions that produce light. There are certain species of jellyfish that are able to bioluminesce or glow for instance. But these types of reactions would essentially have light as a product; they wouldn’t require light in order to react.

The next answer choice is about an increase in temperature. There are plenty of examples of reactions that are initiated by absorbing energy from an increase in temperature, but we’re specifically talking about reactions that are initiated by absorbing energy from light. Our next answer choice says that photochemical reactions do not involve the transfer of electrons. Well, it turns out that there are plenty of examples of photochemical reactions that do involve the transfer of electrons. For example, when you shine a light on silver chloride, electrons are transferred from the chloride ions to the silver ions. But whether or not there is a transfer of electrons is not the definition of a photochemical reaction. Photochemical reactions are simply reactions that are initiated by absorbing energy from light.

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