Advanced Placement (AP) Chemistry Practice Exam

What is gravimetric analysis used for?

1. Identifying the oldest substance in a mixture

2. Determining the total volume of a solution

3. Determining the amount of a species by converting it to a precipitate

4. Measuring the concentration of ions in solution

The correct answer is: Determining the amount of a species by converting it to a precipitate

Gravimetric analysis is a quantitative method used in chemistry to determine the amount of a specific substance by converting it into a solid precipitate. This technique involves the formation of an insoluble compound from the analyte of interest. Once the precipitate is formed, it can be isolated by filtration, washed, dried, and then weighed. The mass of the precipitate can be used to calculate the amount of the original substance in the sample, often with high precision. This method is particularly useful because it allows for accurate and reliable measurements and is based on the law of conservation of mass. The process typically involves steps such as dissolution of the sample, precipitation of the target compound, and careful handling to minimize loss during weighing. Therefore, gravimetric analysis is highly valued for its ability to determine the mass of a known compound that correlates to the original amount of the species present in the sample.