Final answer:
Option B, the mass of a penny, is an inexact quantity because it requires measurement which is subject to some degree of uncertainty.
Step-by-step explanation:
The concept of exact and inexact quantities in chemistry is important to distinguish between those values that can be determined with absolute certainty and those that require measurement and are subject to some degree of uncertainty. When we consider the choices given, we need to identify whether each value is a defined quantity or the result of a measurement that could have a variation.
- The number of people in your chemistry class can change and therefore must be counted. The count is an exact quantity as long as the number does not change during counting.
- The mass of a penny requires measurement and is an inexact quantity. This is because when measuring mass, the actual measure can vary slightly due to various factors including measurement uncertainty.
- The number of grams in a kilogram is a defined value, where by definition, 1 kilogram is exactly 1000 grams. This is an exact quantity.
Given this information, the inexact quantity among the given options is The mass of a penny (Option B).