A Level Chemistry OCR Practice Exam

How is volatility defined in chemistry?

1. The ability of a solid to dissolve in a liquid

2. The ease with which a liquid turns into a gas

3. The rate at which a reaction occurs

4. The tendency of a substance to form a precipitate

The correct answer is: The ease with which a liquid turns into a gas

Volatility in chemistry is defined as the ease with which a liquid turns into a gas. This characteristic primarily relates to the intermolecular forces present in the liquid; when these forces are weak, the molecules can escape into the vapor phase more readily, indicating higher volatility. For instance, substances like acetone and alcohol are highly volatile due to their relatively weak intermolecular forces, allowing them to evaporate quickly, whereas substances like water, which has stronger hydrogen bonding, exhibit lower volatility. Understanding volatility is important in various applications, including distillation and the formulation of perfumes and volatile organic compounds. The other definitions do not pertain to volatility. The ability of a solid to dissolve in a liquid relates to solubility, the rate of a reaction pertains to kinetic chemistry, and the tendency to form a precipitate is associated with precipitation reactions rather than volatility. Therefore, the correct answer aligns precisely with the concept of volatility in chemistry.