Dilution
Dilution refers to the process of reducing the concentration of a solution by adding more solvent. This is typically done to decrease the strength or intensity of a solution, making it less concentrated. It is commonly achieved by adding more solvent to the original solution, resulting in a larger volume with a reduced concentration of the solute.
3 Key excerpts on "Dilution"
eBook - ePub- John Kenkel(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...This means that an analytical balance must be used to weigh the chemical (if the solute is a pure solid), an accurate pipet must be used to measure the volume of a solution of the chemical (if the chemical is already in solution), and a volumetric flask must be used to measure the total solution volume in order to know that just the correct amount of solvent has been added. (See Chapter 2 for a description of the volumetric flask and its use.) However, if the solution concentration need not be known accurately, then any balance, or any type of liquid transfer glassware if the solute is already in solution, would work, and a volumetric flask need not be used. With these thoughts in mind, we proceed with a series of discussions giving specific instructions as to calculations and methods used in a variety of situations involving various concentration units. 3.2 Dilution One method of preparing solutions, as alluded to in the last section, is by Dilution, i.e., the solute is already in solution, but a lower concentration of it is called for. Regardless of the units with which the concentration (or volume) is expressed, the general calculation and method of preparation is the same. The calculation uses the following formula: C B × V B = C A × V A (3.1) in which “C” refers to “concentration,” “V” is “volume,” “B” refers to “before Dilution,” and “A” to “after Dilution.” The concentration of the solution before Dilution times its volume is equal to the concentration of the solution after Dilution times its volume. The concentrations before and after Dilution must be known, and the volume after Dilution must be known. The volume before Dilution is being calculated in order to know how much of the more concentrated solution to measure out and dilute. The units of concentration must be the same on both sides of the equation (e.g., percent, molarity, normality, etc.)...
eBook - ePub- Jeffrey Gaffney, Nancy Marley(Authors)
- 2017(Publication Date)
- Elsevier(Publisher)
...An aqueous solution consists of at least two components, the solvent (water) and the solute. The chemical properties and behavior of solutions are determined by their composition. There are several methods used to specify the composition of a solution. These will all be discussed in detail in Chapter 12, but the most useful method in chemistry is to define the concentration of the solute in the solution as the amount of solute per unit volume of the total solution. The SI units of concentration would be; moles per cubic meter (mol/m 3). However, since 1 m 3 = 0.001 L, this unit is inconvenient for practical use in laboratory chemical reactions. Instead, the concentration unit of molarity (M) is used. Molarity is defined as the number of moles of solute per liter of solution. Molarity M = moles of solute mol liters of solution L (11) It is important to note that the molarity of a solution is defined as the number of moles of solute per liter of solution, not as the number of moles of solute per liter of solvent. This is because the solute adds volume to the solution when it is added to a measured volume of water. So, when you add a chemical substance to water, the volume of the resulting solution will be different than the original volume of the water. To avoid this problem, chemists make up solutions in volumetric flasks, which are very accurately calibrated to contain a precise volume at a particular temperature. The solute is added to the flask first and then water is added until the solution reaches the calibrated etched mark on the neck of the flask (Fig. 4.8). Fig. 4.8 A 500 mL volumetric flask. To make 500 mL of an aqueous solution, a measured amount of solute is added to the flask...
- Kevin Reel, Derrick C. Wood, Scott A. Best(Authors)
- 2014(Publication Date)
- Research & Education Association(Publisher)
...It is your job to be a “unit translator,” because it is an essential skill to convert between the various units. The most important part to watch with the different units is the use of the terms solute, solvent, and solution. If you know what these terms are and what they represent, you will be well on your way to converting between the different units. The most common units of concentration are molarity, molality, mass percent, and mole fraction. Molarity Molarity (M) describes concentration as the moles of solute per liter of solution. It is the most common unit used by chemists to express concentration due to the ease of measuring out a given volume of solution and knowing how many moles of the solute is available to react. However, because the volume of a solution is dependent upon the temperature, the concentration of a solution will vary slightly based on the temperature conditions. Chemists also use brackets to express molar concentration, so [MgCl 2 ] would specifically mean the molar concentration of an MgCl 2 solution. Also, when a solute dissolves in solution, you can easily determine the molar concentrations of the dissolved species based on simple stoichiometry. EXAMPLE: What are the concentrations of the ions present in a 1.5 molar MgCl 2 solution? SOLUTION: The balanced dissolution equation is: The mole ratio is 1:1:2, and thus: Mole Fraction Mole fraction (X) is a ratio of the moles of the solute compared to the total number of moles of all of the components in the solution. Mole fractions are typically used when working with vapor pressure lowering explained by Raoult’s law. Nonideal Solutions • Ideal solutions follow Raoult’s law...
