Chemistry
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.
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7 Key excerpts on "Dilution"
eBook - ePub- Wayne R. Ott(Author)
- 2018(Publication Date)
- Routledge(Publisher)
8 Dilution of Pollutants Polluters discharge chemicals into the environment to dispose of them. Environmental pollution becomes a problem to society because such chemicals sometimes do not disappear. In some cases, such as the pesticide DDT, they are sufficiently inert, or persistent, to remain in the environment for many years. However, discharging a chemical into the environment usually reduces its adverse effects by reducing its concentration (quantity of chemical per unit volume). Concentration reduction is achieved whenever a particular quantity of a chemical (the pollutant) mixes with some other material (the carrier medium), thereby becoming diluted. Dilution is the process by which the molecules of a substance become distributed over a larger physical volume than they formerly occupied. Dilution always accompanies the formal process of diffusion (Chapter 6), because the molecules in a diffusion process tend to spread out and occupy an ever-increasing volume. However, Dilution also can occur in processes that do not primarily involve diffusion, such as the simple mechanical mixing of one chemical liquid with another. For example, if two chemically unreactive liquids are combined together in one container and shaken until they are uniformly mixed, the volume of the resulting mixture will be the sum of the volumes of the two original constituents, and each original constituent will become diluted. Dilution occurs in a large number of common everyday examples: introduction of syrup flavoring when one prepares a milkshake; addition of pigments to raw base paint to give it color; insertion of drops of medicine into a glass of water. Dilution also occurs when concentrated soap is added to a bucket of water for scrubbing the floor. It occurs when table salt is dissolved in hot water prior to cooking rice
eBook - PDF- Leo J. Malone, Theodore O. Dolter(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
The same number of moles are pres- ent before the Dilution and afterward. Though it goes beyond the scope of this text, this concept can be stretched to allow calculations when the Dilution is not occurring with water but instead with a more dilute solution of the compound. For instance, if you wanted to turn your 1.0 M NH 3 into 3.0 M NH 3 by adding 9.0 M NH 3 , determining the total number of moles before and after the Dilution, and then converting into the M * V relationship, would allow you to solve the problem. SYNTHESIS Dilution is a process that occurs frequently in lab. Why so prevalent? Because manufacturers find that it is more convenient to produce and ship solutions that are concentrated. It makes a more convenient use of space and weight and costs less. Furthermore, end users can use the Dilution formula to scale-down the concentrations to whatever value is needed for their particular use. We can always dilute, but without the original solute, we can’t make com- mercial solutions more concentrated. As a result, acids are sold at very high concentrations (18 M for H 2 SO 4 , 12 M for HCl). Hence, there are numerous safety procedures in place whenever we deal with commercial bottles.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2019(Publication Date)
- Openstax(Publisher)
If the guard digit had not been retained, the final calculation for the mass of NaCl would have been 77.1 g, a difference of 0.3 g. In addition to retaining a guard digit for intermediate calculations, rounding errors may also be avoided by performing computations in a single step (see Example 3.18). This eliminates intermediate steps so that only the final result is rounded. EXAMPLE 3.18 Determining the Volume of Solution Containing a Given Mass of Solute In Example 3.16, the concentration of acetic acid in white vinegar was determined to be 0.839 M. What volume of vinegar contains 75.6 g of acetic acid? Solution First, use the molar mass to calculate moles of acetic acid from the given mass: Then, use the molarity of the solution to calculate the volume of solution containing this molar amount of solute: Combining these two steps into one yields: Check Your Learning What volume of a 1.50-M KBr solution contains 66.0 g KBr? 140 3 • Composition of Substances and Solutions Access for free at openstax.org Answer: 0.370 L Dilution of Solutions Dilution is the process whereby the concentration of a solution is lessened by the addition of solvent. For example, a glass of iced tea becomes increasingly diluted as the ice melts. The water from the melting ice increases the volume of the solvent (water) and the overall volume of the solution (iced tea), thereby reducing the relative concentrations of the solutes that give the beverage its taste ( Figure 3.16). FIGURE 3.16 Both solutions contain the same mass of copper nitrate. The solution on the right is more dilute because the copper nitrate is dissolved in more solvent. (credit: Mark Ott) Dilution is also a common means of preparing solutions of a desired concentration. By adding solvent to a measured portion of a more concentrated stock solution, a solution of lesser concentration may be prepared.
eBook - PDF- David A. Ucko(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
Dilution calculations are based on the fact that the number of moles of solute taken from the stock solution and the number of moles of solute in the diluted solution are the same. More solvent is present in the final solution, but the diluted solution still contains the exact amount of solute that was transferred from the stock solution. Thus, moles of the solute (initial) = moles of solute (final) Since many concentrations are expressed in molarity, this equation can also be written as In abbreviated form, this relationship is M, x V, = M 2 x V 2 where Mi and V x are the initial values of the molarity and volume, and M 2 and V 2 are the final values. (The units for V x and V 2 must be the same, but need not be expressed in liters.) A similar equation can be written for concentrations expressed as weight-volume percent, since the number of grams of solute must also stay the same during Dilution. Consider the Dilution of hydrochloric acid, which is available in bottles as an aqueous 12 M solution. To find the volume of this stock solution needed to make 2.00 L of 0.50 M HC1, we set up the problem as follows. stock solution diluted solution liter of solution (initial) x liters of solution (initial) liter of solution (final) x liters of solution (final) 428 moles of solute moles of solute SOLUTIONS / 13.9 Dilution OF SOLUTIONS U N K N O W N GIVEN C O N N E C T I O N Vi, volume of 12 M = M, M, x V, = M 2 x V 2 12 M HC1 0.50 M = M 2 2.00 L = V 2 The molarity of the concentrated stock solution is The needed volume of this solution, Vi, is unknown. The molarity, M 2 , and volume, V 2 , of the diluted solution are both given.
eBook - ePub- John Kenkel(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
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.). The units of volume are also the same on both sides.
eBook - PDF- Alberto Patiño Douce(Author)
- 2011(Publication Date)
- Cambridge University Press(Publisher)
11 Dilute solutions The focus of this chapter is on liquid solutions in which one component is present in much greater abundance, say at least one order of magnitude greater, than all others. Examples that underscore the importance of this type of solutions include seawater, and natural terrestrial waters in general, but one can imagine more exotic possibilities, such as hydrocarbon-based solutions on Titan’s surface and ammonia-based solutions in its interior. What all of these examples share is the fact that it is convenient to make a distinction between dilute solutes that may not be liquid in their standard states, and a liquid solvent that is generally close to being in its standard state. Depending on the nature of the solvent and of the solutes the latter may exist as electrically neutral chemical species, as ions, or as a combination of both. Solutions in which solutes dissociate into ions are known as electrolyte solutions. Among these, those in which water is the solvent are by far the most important ones, at least in terrestrial environments. The chapter emphasizes aqueous electrolyte solutions, but virtually all of the thermodynamic framework is applicable to any type of dilute solution. We begin with a discussion of dilute solutions in general, and shift the focus to electrolyte solutions in Section 11.3. 11.1 Some properties of dilute solutions In our discussions so far on the thermodynamic properties of solutions we have made no distinction between the treatment of the different solution components. All our equations have been symmetric, in the sense that we could interchange the components and arrive at the same final result. This was true whether the solution was above or below its critical mixing point (Section 7.1). In the latter case we considered two distinct subcritical phases (for binary systems), and we allowed for the possibility that one or the other, or both, could exist within some region of interest.
- Frank H. Stephenson(Author)
- 2016(Publication Date)
- Academic Press(Publisher)
Chapter 2Solutions, Mixtures, and Media
Abstract
Whether it is an organism or an enzyme, most biological activities function at their optimum only within a narrow range of environmental conditions. From growing cells in culture to sequencing of a cloned DNA fragment or assaying an enzyme's activity, the success or failure of an experiment can hinge on paying careful attention to a reaction's components. This section outlines the mathematics involved in making solutions. This chapter covers how to make Dilutions to new concentrations of percent, molarity, factor of X, and normality. This chapter shows how to calculate pH and how the Henderson–Hasselbalch equation is used to prepare a buffer having a particular desired pH.Keywords
Acid; Acid dissociation constant; Addition property of equality; Base; Bronsted acid; Bronsted base; Conjugate acid; Conjugate base; Dilution; Dimensional analysis; Equilibrium; Formula weight; Gram molecular weight; Henderson–Hasselbalch equation; Molarity; Molecular weight; Multiplication property of equality; Normality; Percent; pHIntroduction
Whether it is an organism or an enzyme, most biological activities function at their optimum only within a narrow range of environmental conditions. From growing cells in culture to sequencing of a cloned DNA fragment or assaying an enzyme's activity, the success or failure of an experiment can hinge on paying careful attention to a reaction's components. This section outlines the mathematics involved in making solutions.2.1. Calculating Dilutions: A General Approach
Concentration is defined as an amount of some substance per a set volume:concentration =amount volumeMost laboratories have found it convenient to prepare concentrated stock solutions of commonly used reagents, those found as components in a large variety of buffers or reaction mixes. Such stock solutions may include 1 M Tris, pH 8.0, 500 mM EDTA, 20% sodium dodecylsulfate (SDS), 1 M MgCl2 , and any number of others. A specific volume of a stock solution at a particular concentration can be added to a buffer or a reagent mixture so that it contains that component at some concentration less than that in the stock. For example, a stock solution of 95% ethanol can be used to prepare a solution of 70% ethanol. Since a higher percent solution (more concentrated) is being used to prepare a lower percent (less concentrated) solution, a Dilution
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