Concentrations of Solutions (4.1.3) Flashcards
• The concentration of a solution is measured as the amount of solute per volume.
• The concentration of a solution is measured as the amount of solute per volume.
• Knowing the concentration of a solution allows one to calculate the concentrations of solutions made by diluting the original solution.
• Knowing the concentration of a solution allows one to calculate the concentrations of solutions made by diluting the original solution.
• Several different concentration units are used by chemists.
• Several different concentration units are used by chemists.
The concentration of a solution is measured as the amount of solute per volume. Molarity is the concentration unit most frequently used by chemist. One molar is one mole of solute per liter of solution. A solution with a known molarity can be prepared by dissolving a known mass of solute in enough water to fill a 200 mL volumetric flask. The molarity of this solution can be calculated by converting the mass of solute to moles of solute (using the molar mass of the solute) and dividing by the volume in liters. The moles of a given ion in a given quantity of solution can be calculated knowing the stoichiometry of the solute. For example, every mole of sodium sulfate yields two moles of sodium ion (Na+). Therefore, 1.86 moles of sodium ion are present in one liter of a 0.930 M solution of sodium sulfate. Dilution involves making a less concentrated solution by adding solvent to a given amount of a more concentrated solution. Knowing the concentration of a solution allows one to calculate the concentrations of solutions made by diluting the original solution. Problem: How much of a 0.930 M solution is needed to make 250. mL of a 0.10 M Na2SO4 solution? This problem can be solved by noting that the number of moles of solute present before diluting is equal to the number of moles present after the solution is diluted. The number of moles is equal to the molarity (M) multiplied by the volume (V). Therefore, M1V1 = M2V2. Solving for V1 yields the volume of the original solution required to make the desired solution.
The concentration of a solution is measured as the amount of solute per volume. Molarity is the concentration unit most frequently used by chemist. One molar is one mole of solute per liter of solution. A solution with a known molarity can be prepared by dissolving a known mass of solute in enough water to fill a 200 mL volumetric flask. The molarity of this solution can be calculated by converting the mass of solute to moles of solute (using the molar mass of the solute) and dividing by the volume in liters. The moles of a given ion in a given quantity of solution can be calculated knowing the stoichiometry of the solute. For example, every mole of sodium sulfate yields two moles of sodium ion (Na+). Therefore, 1.86 moles of sodium ion are present in one liter of a 0.930 M solution of sodium sulfate. Dilution involves making a less concentrated solution by adding solvent to a given amount of a more concentrated solution. Knowing the concentration of a solution allows one to calculate the concentrations of solutions made by diluting the original solution. Problem: How much of a 0.930 M solution is needed to make 250. mL of a 0.10 M Na2SO4 solution? This problem can be solved by noting that the number of moles of solute present before diluting is equal to the number of moles present after the solution is diluted. The number of moles is equal to the molarity (M) multiplied by the volume (V). Therefore, M1V1 = M2V2. Solving for V1 yields the volume of the original solution required to make the desired solution.
Several other concentration units are used by chemists.
One molal is one mole of solute per kilogram of solvent.
Molality differs from molarity in two ways: the denominator is in terms of mass, not volume; and the denominator involves solvent, not total solution.
Percent by mass is the mass of solute divided by the total
mass of solution, times 100%. Percent by mass is also called weight % or % (w/w). Parts per million (ppm) is similar to percent by mass, but the fraction is multiplied by 1,000,000 rather than 100%. Parts per million is useful for measuring extremely dilute concentrations.
Several other concentration units are used by chemists.
One molal is one mole of solute per kilogram of solvent.
Molality differs from molarity in two ways: the denominator is in terms of mass, not volume; and the denominator involves solvent, not total solution.
Percent by mass is the mass of solute divided by the total
mass of solution, times 100%. Percent by mass is also called weight % or % (w/w). Parts per million (ppm) is similar to percent by mass, but the fraction is multiplied by 1,000,000 rather than 100%. Parts per million is useful for measuring extremely dilute concentrations.
