Concentration of substance in analytical chemistry is expressed in which of the following units?

The correct choice is significant because it highlights common units used to express the concentration of substances in analytical chemistry. Molarity is a fundamental unit that indicates the number of moles of solute per liter of solution, reflecting how concentration relates to volume, which is crucial for many analytical procedures.

Parts per million (ppm) and parts per billion (ppb) are also widely used units presented in this choice. Ppm is equivalent to milligrams of solute per liter of solution (mg/L) and is particularly useful for expressing very dilute solutions, while ppb corresponds to micrograms of solute per liter (µg/L). These units are essential in fields such as environmental chemistry, where detection of trace amounts of pollutants is necessary.

The presence of all three units – molarity, ppm, and ppb – in this option demonstrates a comprehensive understanding of concentration measurement in various contexts, making it a useful option for analytical chemistry scenarios. Other choices may include combinations of units that are less commonly used together or may lack the versatility found in ppm and ppb relative to the concentrations being measured.