Which of the following solutions has the higher molarity? (a) 10 ppm KI in water or 10,000 ppb KBr in water

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Understand the units: ppm (parts per million) and ppb (parts per billion) are common units used to express concentration. 1 ppm is equivalent to 1 mg of solute per liter of solution, and 1 ppb is equivalent to 1 extmu g of solute per liter of solution.

Convert ppm and ppb to molarity: To convert ppm to molarity, divide the ppm value by the molar mass of the solute and multiply by 1000 to convert mg to grams. For ppb, divide the ppb value by the molar mass of the solute and multiply by 1,000,000 to convert extmu g to grams.

Calculate the molar mass of KI and KBr: Use the periodic table to find the atomic masses of K (potassium), I (iodine), and Br (bromine). Add the atomic masses to get the molar mass of KI and KBr.

Apply the conversion to both solutions: Use the molar mass of KI to convert 10 ppm of KI to molarity. Similarly, use the molar mass of KBr to convert 10,000 ppb of KBr to molarity.

Compare the molarities: The solution with the higher resulting molarity value will be the one with the higher concentration.

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Key Concepts

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

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (mol/L) and is crucial for comparing the concentration of different solutions. Understanding molarity allows for the calculation of how much solute is present in a given volume of solvent, which is essential for determining which solution is more concentrated.

Parts per million (ppm) and parts per billion (ppb)

Parts per million (ppm) and parts per billion (ppb) are units used to express very dilute concentrations of substances. 1 ppm is equivalent to 1 mg of solute per liter of solution, while 1 ppb is equivalent to 1 µg of solute per liter. Converting these units to molarity requires knowledge of the molar mass of the solute, which is necessary for comparing the concentrations of the two solutions in the question.

Conversion between concentration units

To compare the molarity of solutions expressed in different concentration units, it is essential to convert them to a common unit. This involves using the definitions of ppm and ppb to find the mass of solute in a specific volume of solution, and then converting that mass to moles using the molar mass. This process allows for a direct comparison of the concentrations of the two solutions in the question.