How will you separate gasoline from water?
A. Decantation
B. Filtration
C. Distillation
D. Evaporation
The correct answer and explanation is:
The correct answer is C. Distillation.
Gasoline and water form a mixture that is immiscible, meaning they do not mix uniformly. They separate into two distinct layers because gasoline is less dense than water and is also volatile. To separate gasoline from water, distillation is the most appropriate method.
Distillation is a process that separates components in a mixture based on their different boiling points. Water has a boiling point of 100 degrees Celsius, while gasoline is a mixture of hydrocarbons with lower boiling points, typically between 30 and 200 degrees Celsius depending on the exact composition. During distillation, the mixture is heated gradually. Since gasoline has a lower boiling point, it vaporizes first. The gasoline vapor is collected and then cooled to condense back into liquid form, leaving the water behind.
Decantation involves pouring off the top layer of liquid after the two phases have separated by gravity. While this could separate the two liquids partially because gasoline floats on water, it may not result in a pure separation, and some water might remain mixed with gasoline.
Filtration is used to separate solids from liquids and is not effective for separating two immiscible liquids like gasoline and water.
Evaporation involves heating a liquid until it vaporizes, but it is not a practical method here because gasoline is volatile and flammable, making evaporation unsafe and inefficient. Moreover, evaporation would not easily separate gasoline from water since both can vaporize, and it would be difficult to capture the gasoline vapor without loss.
Therefore, distillation is the best method because it efficiently separates gasoline from water by exploiting their difference in boiling points, allowing for collection of purified gasoline while leaving water behind. This method is widely used in laboratories and industries for separating liquid mixtures with different volatilities.