A Level Chemistry OCR Practice Exam

What does reduction refer to in terms of electron transfer?

1. Loss of electrons or an increase in oxidation number

2. Gain of protons

3. Gain of electrons or a decrease in oxidation number

4. No change in electron configuration

The correct answer is: Gain of electrons or a decrease in oxidation number

Reduction is defined in terms of electron transfer as the gain of electrons, which results in a decrease in the oxidation number of an element. This process involves an increase in the electron density around an atom, making it more negative. When reduction occurs, the substance that gains electrons is referred to as the reducing agent, while the substance that loses electrons undergoes oxidation. Reduction plays a pivotal role in redox reactions, where two processes—oxidation and reduction—happen simultaneously. A clear understanding of this concept is crucial, as it helps in predicting the behavior of substances in chemical reactions, especially in organic and inorganic chemistry. The other options describe processes that are not aligned with the definition of reduction. For instance, the loss of electrons or an increase in oxidation number signifies oxidation, whereas the gain of protons does not pertain directly to the transfer of electrons in reduction. Lastly, stating no change in electron configuration does not reflect the dynamic nature of reduction, where the gain of electrons certainly alters the configuration. Thus, the accurate representation of reduction aligns with the understanding that it involves the gain of electrons and a decrease in oxidation number.