The correct option for the factor that primarily affects the electrical conductivity of gases under standard conditions is: **C. The presence of impurities or ionizing radiation** ### Detailed Explanation 1. **Understanding Electrical Conductivity in Gases**: - Electrical conductivity refers to a material's ability to conduct electric current. In gases, this is generally very low because gas molecules are far apart, and there are few free charge carriers (like electrons or ions) available to carry the current. - For a gas to conduct electricity, it must have charged particles (ions or free electrons). These can be created through processes such as ionization, which can occur due to high temperatures, strong electric fields, or the presence of radiation. 2. **Why Option C is Correct**: - **Presence of Impurities**: When impurities are introduced into a gas, they can provide additional charge carriers. For example, adding a small amount of a conductive gas (like water vapor or carbon dioxide) can increase the overall conductivity of the gas mixture. - **Ionizing Radiation**: Ionizing radiation (like ultraviolet light or X-rays) can ionize gas molecules, creating free electrons and positive ions. This process significantly increases the number of charge carriers, thus enhancing the gas's conductivity. - Under standard conditions, the presence of these impurities or radiation is a more direct and impactful factor in increasing conductivity compared to other options. 3. **Why the Other Options are Weaker**: - **A. The temperature of the gas**: While temperature can affect conductivity (higher temperatures can increase the energy of gas molecules, potentially leading to more ionization), it is not the primary factor under standard conditions. In many cases, gases remain non-conductive at standard temperatures unless ionization occurs. - **B. The pressure of the gas**: Increasing pressure can lead to more collisions between gas molecules, which might increase the likelihood of ionization. However, under standard conditions, the effect of pressure on conductivity is less significant than the presence of impurities or ionizing radiation. - **D. The molecular weight of the gas**: The molecular weight can influence the behavior of gas molecules, but it does not directly affect the conductivity. Heavier gases may have slower-moving molecules, which could reduce the likelihood of ionization, but this is a secondary effect compared to the presence of charge carriers. ### Summary of Key Points - **Electrical conductivity in gases is primarily influenced by the availability of charge carriers**. - **Impurities and ionizing radiation significantly enhance conductivity by providing additional ions and electrons**. - **Temperature and pressure can influence conductivity but are not the primary factors under standard conditions**. - **Molecular weight does not directly affect conductivity**. ### Revision Summary - The primary factor affecting electrical conductivity in gases is the presence of impurities or ionizing radiation (Option C). - Impurities introduce additional charge carriers, while ionizing radiation creates free electrons and ions. - Temperature and pressure have secondary effects on conductivity. - Molecular weight does not play a significant role in determining the conductivity of gases.