Final answer:
The human body excretes about 2.0 g of potassium per day via the urine, which is equivalent to 2000 mg.
Step-by-step explanation:
The student asked how to express the mass of potassium excreted by the human body in milligrams. The question provided the information that the human body normally excretes about 2.0 g of potassium per day via the urine. To convert grams to milligrams, we multiply the mass by 1000. Therefore, the mass of potassium excreted in mg is 2.0 g * 1000 mg/g = 2000 mg.