Residues of the herbicide atrazine (C₈H₁₄ClN₅) in water can be detected at concentrations as low as 0.050 µg/L. Express this concentration of atrazine in the following units: (a) Parts per billion (assume a solution density of 1.00 g/mL)

Verified step by step guidance

1. Understand that parts per billion (ppb) is a way to express very dilute concentrations of substances. It is defined as the mass of the solute divided by the mass of the solution, multiplied by 10^9.
2. Since the density of the solution is given as 1.00 g/mL, we can assume that 1 L of the solution has a mass of 1000 g (since 1 L = 1000 mL).
3. Convert the concentration from micrograms per liter (µg/L) to grams per liter (g/L) by recognizing that 1 µg = 10^-6 g. Therefore, 0.050 µg/L is equivalent to 0.050 x 10^-6 g/L.
4. Calculate the mass of atrazine in grams in 1 L of solution, which is 0.050 x 10^-6 g.
5. To find the concentration in ppb, divide the mass of atrazine in grams by the mass of the solution in grams (1000 g), and then multiply by 10^9 to convert to ppb.

Key Concepts

Concentration Units

Concentration is a measure of the amount of a substance in a given volume of solution. Common units include molarity (moles per liter), mass per volume (grams per liter), and parts per billion (ppb). Understanding how to convert between these units is essential for accurately expressing the concentration of substances in solutions.

Parts Per Billion (ppb)

Parts per billion (ppb) is a unit of measurement used to describe very dilute concentrations of substances. It indicates how many parts of a substance are present in one billion parts of the total solution. For example, 1 ppb means 1 microgram of a substance in 1 liter of water, making it crucial for environmental and health-related assessments.

Density of Water

The density of water is typically 1.00 g/mL at standard conditions, which simplifies calculations involving mass and volume. This property allows for straightforward conversions between mass (in grams) and volume (in milliliters or liters), facilitating the determination of concentrations in various units, including ppb.