Because the solute occupies space in the solution, the volume of the solvent needed is almost always less than the desired volume of solution.
For example, if the desired volume were 1. The solution contains Given: mass of solute and volume of solution. Calculate the molarity of the solution by dividing the number of moles of solute by the volume of the solution in liters.
Molarity is the number of moles of solute per liter of solution, so the molarity of the solution is. What is the molar concentration of ammonium dichromate? We then convert the number of moles of solute to the corresponding mass of solute needed.
The so-called D5W solution used for the intravenous replacement of body fluids contains 0. Calculate the mass of glucose necessary to prepare a mL pouch of D5W. Glucose has a molar mass of Given: molarity, volume, and molar mass of solute. A We must first calculate the number of moles of glucose contained in mL of a 0. B We then convert the number of moles of glucose to the required mass of glucose:.
Another solution commonly used for intravenous injections is normal saline, a 0. Calculate the mass of sodium chloride needed to prepare mL of normal saline solution. A solution of a desired concentration can also be prepared by diluting a small volume of a more concentrated solution with additional solvent. A stock solution is a commercially prepared solution of known concentration and is often used for this purpose. Diluting a stock solution is preferred because the alternative method, weighing out tiny amounts of solute, is difficult to carry out with a high degree of accuracy.
Dilution is also used to prepare solutions from substances that are sold as concentrated aqueous solutions, such as strong acids. It requires calculating the number of moles of solute desired in the final volume of the more dilute solution and then calculating the volume of the stock solution that contains this amount of solute. Remember that diluting a given quantity of stock solution with solvent does not change the number of moles of solute present.
The relationship between the volume and concentration of the stock solution and the volume and concentration of the desired diluted solution is therefore. What volume of a 3. Given: volume and molarity of dilute solution. A The D5W solution in Example 4. The molarity of a solution is the number of moles of solute per liter of solution; e.
The molality of a solution is the number of moles of solute per 1, grams of solvent; a solution prepared by dissolving The mole fraction of a solution is the ratio of moles of solute to the total number of moles in the solution.
Since ionic compounds, such as sodium chloride, NaCl, do not occur as molecules, their concentrations cannot be expressed in terms of molarity, molality, or mole fraction. Instead, the concentration of an ionic compound in solution may be given by its formality, the number of gram-formula weights of the compound per liter of solution; e. In considering the reactions of certain solutions in combination, for example the neutralization of acids and bases, a useful expression of the concentration is the normality of each solution, the number of gram-equivalent weights of solute per liter of solution see equivalent weight ; e.
Note: this document will print in an appropriately modified format?? Solutions are homogeneous single-phase mixtures of two or more components. For convenience, we often refer to the majority component as the solvent ; minority components are solutes. But there is really no fundamental distinction between them. Details about the special factors that affect the rate of reactions carried out in solutions as opposed to the gas phase are described here.
Solutions play a very important role in Chemistry because they allow intimate and varied encounters between molecules of different kinds, a condition that is essential for rapid chemical reactions to occur. Several more explicit reasons can be cited for devoting a significant amount of effort to the subject of solutions:.
We usually think of a solution as a liquid made by adding a gas, a solid or another liquid solute in a liquid solvent. Actually, solutions can exist as gases and solids as well.
Solid solutions are very common; most natural minerals and many metallic alloys are solid solutions. Still, it is liquid solutions that we most frequently encounter and must deal with. Actually, this is not strictly correct, since all substances have at least a slight tendency to dissolve in each other. This raises two important and related questions: why do solutions tend to form in the first place, and what factors limit their mutual solubilities?
Concentration is a general term that expresses the quantity of solute contained in a given amount of solution. Various ways of expressing concentration are in use; the choice is usually a matter of convenience in a particular application.
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