Identify which liquid will have a higher vapour pressure at 90℃ if the boiling points of two liquids A and B are 140℃ and 180℃, respectively.

Explanation

To determine which liquid has a higher vapor pressure at 90℃, we can use the relationship between vapor pressure and boiling point.

A liquid with a lower boiling point generally has a higher vapor pressure at a given temperature. This is because a lower boiling point indicates that the liquid requires less energy (temperature) to convert to vapor, meaning it will have more molecules in the vapor phase at any temperature below its boiling point.

In this case:

• Liquid A has a boiling point of 140℃.
• Liquid B has a boiling point of 180℃.

Since Liquid A has a lower boiling point than Liquid B, it will have a higher vapor pressure at 90℃. This is because Liquid A is closer to its boiling point than Liquid B at this temperature, so more of its molecules will be in the vapor phase, resulting in higher vapor pressure.

Therefore, Liquid A will have a higher vapor pressure at 90℃ than Liquid B.