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The concentration of gold in seawater has been reported to be between 5 ppt (parts per trillion) and 50 ppt. Assuming that seawater contains 13 ppt of gold, calculate the number of grams of gold contained in 1.0 * 10^3 gal of seawater.
Ch.13 - Properties of Solutions
Chapter 13, Problem 98b
Acetonitrile (CH3CN) is a polar organic solvent that dissolves a wide range of solutes, including many salts. The density of a 1.80 M LiBr solution in acetonitrile is 0.826 g/cm3. Calculate the concentration of the solution in (b) mole fraction of LiBr,
Verified step by step guidance1
insert step 1> Calculate the molar mass of LiBr by adding the atomic masses of lithium (Li) and bromine (Br).
insert step 2> Use the molarity (1.80 M) to find the moles of LiBr in 1 liter of solution.
insert step 3> Calculate the mass of 1 liter of the solution using its density (0.826 g/cm^3). Remember that 1 liter is equivalent to 1000 cm^3.
insert step 4> Determine the mass of acetonitrile in the solution by subtracting the mass of LiBr (from step 2) from the total mass of the solution (from step 3).
insert step 5> Calculate the mole fraction of LiBr by dividing the moles of LiBr by the total moles of all components in the solution (moles of LiBr and moles of acetonitrile).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molarity
Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. In this case, the 1.80 M LiBr solution indicates that there are 1.80 moles of lithium bromide dissolved in one liter of acetonitrile. Understanding molarity is essential for converting between different concentration units and for calculations involving solutions.
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Mole Fraction
Mole fraction is a way to express the concentration of a component in a mixture, defined as the ratio of the number of moles of that component to the total number of moles of all components in the mixture. To calculate the mole fraction of LiBr in the solution, one must determine the moles of LiBr and the moles of acetonitrile, which requires knowledge of the solution's density and volume.
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Density
Density is defined as mass per unit volume and is crucial for converting between mass and volume in solution calculations. The density of the LiBr solution (0.826 g/cm³) allows us to find the mass of the solution, which can then be used to calculate the number of moles of the solvent and solute. This information is vital for determining the mole fraction of LiBr.
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Related Practice
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The maximum allowable concentration of lead in drinking water is 9.0 ppb. (b) How many grams of lead are in a swimming pool containing 9.0 ppb lead in 60 m3 of water?
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Textbook Question
Acetonitrile (CH3CN) is a polar organic solvent that dissolves a wide range of solutes, including many salts. The density of a 1.80 M LiBr solution in acetonitrile is 0.826 g/cm3. Calculate the concentration of the solution in (a) molality,
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Textbook Question
Two beakers are placed in a sealed box at 25 °C. One beaker contains 30.0 mL of a 0.050 M aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains 30.0 mL of a 0.035 M aqueous solution of NaCl. The water vapor from the two solutions reaches equilibrium. (a) In which beaker does the solution level rise, and in which one does it fall?
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Textbook Question
Two beakers are placed in a sealed box at 25 °C. One beaker contains 30.0 mL of a 0.050 M aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains 30.0 mL of a 0.035 M aqueous solution of NaCl. The water vapor from the two solutions reaches equilibrium. (b) What are the volumes in the two beakers when equilibrium is attained, assuming ideal behavior?
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