Final answer:
Analytical chemistry is the branch of chemistry that would study the amount of mercury present in a soil sample.
Step-by-step explanation:
The branch of chemistry that would study the amount of mercury present in a soil sample is analytical chemistry. Analytical chemistry focuses on separating, identifying, and quantifying chemicals in samples of matter. In this case, an analytical chemist would use complex instruments and techniques to analyze the soil sample and determine the concentration of mercury present.