Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0011% Pb by mass. How much of the water (in mL) contains 150 mg of Pb? (Assume a density of 1.0 g/mL.)

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780137832217

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Determine the mass percentage of Pb in the water sample. This is given as 0.0011%, which means that there are 0.0011 grams of Pb in every 100 grams of water.

Calculate the mass of water needed to contain 150 mg of Pb. Since 0.0011 grams of Pb is present in 100 grams of water, set up a proportion to find the mass of water that would contain 150 mg (0.150 grams) of Pb.

Convert the mass of water from grams to milliliters using the density of water. Given that the density of water is approximately 1.0 g/mL, 1 gram of water corresponds to 1 mL.

Set up the equation based on the proportion and density to solve for the volume of water in milliliters that contains 150 mg of Pb.

Check your calculations to ensure that the units are consistent and the mathematical operations are performed correctly.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mass Percentage

Mass percentage is a way of expressing the concentration of a component in a mixture. It is calculated by dividing the mass of the component by the total mass of the mixture and multiplying by 100. In this case, the mass percentage of lead (Pb) in the water sample is 0.0011%, indicating that for every 100 grams of the sample, there are 0.0011 grams of Pb.

Density

Density is defined as mass per unit volume and is a critical property in chemistry for converting between mass and volume. In this problem, the density of the water is given as 1.0 g/mL, which means that 1 mL of water has a mass of 1 gram. This relationship allows us to convert the mass of lead into the corresponding volume of water.

Unit Conversion

Unit conversion is the process of converting a quantity expressed in one set of units to another. In this question, we need to convert the mass of lead (150 mg) into grams and then use the mass percentage to find the total mass of the water sample that contains this amount of lead. Understanding how to perform these conversions is essential for solving the problem accurately.

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