20 Questions
What concentration of lead in tap water requires certain remedial actions according to the EPA?
15 ppb
If the concentration of lead in tap water is 0.015 ppm, what is the equivalent concentration in ppb?
15 ppb
Assuming a density of 1.00 g/mL for tap water, what mass of lead (in μg) would be contained in a typical glass of water (300 mL) if the lead concentration is 4.5 ppm?
1350 μg
If a 50.0-g sample of industrial wastewater contains 0.48 mg of mercury, what is the concentration of mercury in ppm?
9.6 ppm
In the context of water contamination, what does ppb stand for?
Parts per Billion
What does the EPA require when contaminants reach an unsafe level in unfiltered tap water?
Certain remedial actions
If the concentration of a substance is 250 ppb, what would be the equivalent concentration in ppm?
25 ppm
What is the relationship between parts per million (ppm) and parts per billion (ppb)?
1 ppm = 1000 ppb
If a certain substance has a concentration of 2 ppm in water, how much would be contained in 500 mL of that water?
10 μg
When discussing solute concentrations in water, what does 'Inline water filters' aim to achieve?
Reduce solute concentrations
What remedial actions must be taken according to the EPA when the concentration of lead in tap water reaches 15 ppb?
Certain remedial actions must be taken
If a glass of water (300 mL) contains lead at a concentration of 0.015 ppm, how many micrograms (μg) of lead would it contain?
4.5 μg
Expressing the mercury concentration in the wastewater as 9600 ppb, what would be the equivalent concentration in ppm?
96 ppm
Assuming a concentration of 250 ppb, what would be the equivalent concentration of the substance in ppm?
0.25 ppm
What action does an 'Inline water filter' aim to achieve with respect to solutes in tap water?
Reduce the solute concentration
What is the relationship between parts per million (ppm) and parts per billion (ppb)?
1 ppm = 1000 ppb
'Inline water filters' aim to address which specific issue related to tap water quality?
Solute concentrations
'Parts per million' (ppm) represents a concentration of how many parts per billion (ppb)?
$10^3$ ppb
'Filtered Water Dispenser' machines are primarily aimed at addressing what issue with tap water?
$\text{Solute}$ concentrations in water
$1 \text{ ppb} = \text{how many } \mu \text{g/L}$?
$1 \mu \text{g/L}$
Study Notes
Concentration Units
- Molarity is not the only measure of concentration, and other units are used in various applications for convenience or by convention.
Mass Percentage
- Defined as the ratio of the component's mass to the solution's mass, expressed as a percentage.
- Formula: mass percentage = (mass of component / mass of solution) × 100%
- Also referred to as percent mass, percent weight, weight/weight percent, and other variations.
- Common symbol: % (percent sign)
- Popular concentration unit for consumer products.
Calculation of Percent by Mass
- Example: A 5.0-g sample of spinal fluid contains 3.75 mg of glucose. The percent by mass of glucose in spinal fluid is approximately 0.075%.
- Any mass unit can be used to compute a mass percentage, but the same unit must be used for both the solute and the solution.
Volume Percentage
- Defined as the ratio of the solute volume to the solution volume, expressed as a percentage.
- Formula: volume percentage = (volume of solute / volume of solution) × 100%
- Also referred to as %vol or (v/v)%
- Conveniently measured using common and relatively inexpensive laboratory equipment.
Calculation using Volume Percentage
- Example: Rubbing alcohol (isopropanol) is usually sold as a 70%vol aqueous solution. The density of isopropyl alcohol is 0.785 g/mL.
Mass-Volume Percentage
- A "mixed" percentage unit derived from the mass of solute and the volume of solution.
- Ratio of a solute's mass to the solution's volume, expressed as a percentage.
- Units used for solute mass and solution volume may vary depending on the solution.
- Examples: physiological saline solution (0.9% mass/volume) and blood glucose concentration (milligrams of glucose per deciliter of blood).
Parts per Million and Parts per Billion
- Used to express very low solute concentrations.
- Defined in terms of masses, volumes, or mixed mass-volume units.
- Mass-based definitions: ppm = (mass of solute / mass of solution) × 10^6, ppb = (mass of solute / mass of solution) × 10^9.
- Convenient units for reporting concentrations of pollutants and other trace contaminants in water.### Water Filtration and Contaminants
- In some areas, unfiltered tap water can be unsafe for drinking and cooking due to trace-level concentrations of contaminants.
- Inline water filters reduce the concentration of solutes in tap water.
Measurement of Contaminants
- Parts per million (ppm) is 1000 times greater than parts per billion (ppb).
- 1 ppm = 10^3 ppb.
- To convert from ppb to ppm, divide by 1000.
Calculating Concentration of Contaminants
- To calculate the mass of a contaminant in a given volume of water, use the equation: mass solute = ppb × mass solution × 10^9.
- To convert the mass of a contaminant from grams to micrograms, multiply by 10^6.
Example Problems
- If the concentration of lead in tap water is 15 ppb, it is equivalent to 0.015 ppm.
- At this concentration, a 300 mL glass of water would contain 4.5 μg of lead.
- If a 50.0-g sample of industrial wastewater contains 0.48 mg of mercury, the mercury concentration is 9.6 ppm and 9600 ppb.
Learn how to calculate the amount of isopropyl alcohol present in a rubbing alcohol solution using volume percentage. Practice solving problems involving the concentration of solutions and the density of substances.
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