A Level Chemistry OCR Practice Exam

Which statement about volatility is true?

1. Volatility increases as boiling point decreases

2. Volatility is independent of temperature

3. All liquids have the same volatility

4. Volatility always decreases with an increase in pressure

The correct answer is: Volatility increases as boiling point decreases

Volatility refers to how readily a substance vaporizes. The statement indicating that volatility increases as boiling point decreases is accurate because a lower boiling point means that less energy is required for the molecules to escape into the vapor phase. Therefore, substances with lower boiling points evaporate more easily at a given temperature, demonstrating higher volatility. In contrast, the other statements do not hold true. For example, volatility is not independent of temperature; it typically increases with rising temperature as more molecules gain sufficient energy to escape into the vapor phase. Additionally, different liquids can exhibit significantly different volatilities; therefore, it is incorrect to state that all liquids have the same volatility. Furthermore, while pressure can influence volatility, it is not universally true that volatility always decreases with an increase in pressure, as the behavior can vary with different substances and conditions.