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The major component of a solution is called the solvent. The minor component of a solution is called the solute. By major and minor we mean whichever component has the greater presence by mass or by moles. Sometimes this becomes confusing, especially with substances with very different molar masses. However, here we will confine the discussion to solutions for which the major component and the minor component are obvious. Solutions exist for every possible phase of the solute and the solvent. Salt water, for example, is a solution of solid NaCl in liquid water; soda water is a solution of gaseous CO2 in liquid water, while air is a solution of a gaseous solute (O2) in a gaseous solvent (N2). In all cases, however, the overall phase of the solution is the same phase as the solvent.
A solution is made by dissolving 1.00 g of sucrose (C12H22O11) in 100.0 g of liquid water. Identify the solvent and solute in the resulting solution. Solution Either by mass or by moles, the obvious minor component is sucrose, so it is the solute. Water—the majority component—is the solvent. The fact that the resulting solution is the same phase as water also suggests that water is the solvent. Test Yourself A solution is made by dissolving 3.33 g of HCl(g) in 40.0 g of liquid methyl alcohol (CH3OH). Identify the solvent and solute in the resulting solution. Answer solute: HCl(g); solvent: CH3OH One important concept of solutions is in defining how much solute is dissolved in a given amount of solvent. This concept is called concentration. Various words are used to describe the relative amounts of solute. Dilute describes a solution that has very little solute, while concentrated. describes a solution that has a lot of solute. One problem is that these terms are qualitative; they describe more or less but not exactly how much. In most cases, only a certain maximum amount of solute can be dissolved in a given amount of solvent. This maximum amount is called the solubility of the solute. It is usually expressed in terms of the amount of solute that can dissolve in 100 g of the solvent at a given temperature. Table 11.2 “Solubilities of Some Ionic Compounds” lists the solubilities of some simple ionic compounds. These solubilities vary widely: NaCl can dissolve up to 31.6 g per 100 g of H2O, while AgCl can dissolve only 0.00019 g per 100 g of H2O.
When the maximum amount of solute has been dissolved in a given amount of solvent, we say that the solution is saturated with solute. When less than the maximum amount of solute is dissolved in a given amount of solute, the solution is unsaturated. These terms are also qualitative terms because each solute has its own solubility. A solution of 0.00019 g of AgCl per 100 g of H2O may be saturated, but with so little solute dissolved, it is also rather dilute. A solution of 36.1 g of NaCl in 100 g of H2O is also saturated but rather concentrated. Ideally, we need more precise ways of specifying the amount of solute in a solution. We will introduce such ways in Section 11.2 “Quantitative Units of Concentration”. In some circumstances, it is possible to dissolve more than the maximum amount of a solute in a solution. Usually, this happens by heating the solvent, dissolving more solute than would normally dissolve at regular temperatures, and letting the solution cool down slowly and carefully. Such solutions are called supersaturated solutions and are not stable; given an opportunity (such as dropping a crystal of solute in the solution), the excess solute will precipitate from the solution. It should be obvious that some solutes dissolve in certain solvents but not others. NaCl, for example, dissolves in water but not in vegetable oil. Beeswax dissolves in liquid hexane but not water. What is it that makes a solute soluble in some solvents but not others? The answer is intermolecular interactions. The intermolecular interactions include London dispersion forces, dipole-dipole interactions, and hydrogen bonding (as described in Chapter 10 “Solids and Liquids”). From experimental studies, it has been determined that if molecules of a solute experience the same intermolecular forces that the solvent does, the solute will likely dissolve in that solvent. So, NaCl—a very polar substance because it is composed of ions—dissolves in water, which is very polar, but not in oil, which is generally nonpolar. Nonpolar wax dissolves in nonpolar hexane but not in polar water. This concept leads to the general rule that “like dissolves like” for predicting whether a solute is soluble in a given solvent. However, this is a general rule, not an absolute statement, so it must be applied with care.
Would I2 be more soluble in CCl4 or H2O? Explain your answer. Solution I2 is nonpolar. Of the two solvents, CCl4 is nonpolar and H2O is polar, so I2 would be expected to be more soluble in CCl4. Test Yourself Would C3H7OH be more soluble in CCl4 or H2O? Explain your answer. Answer H2O because both experience hydrogen bonding
In most cases, only a certain maximum amount of solute can be dissolved in a given amount of solvent. This maximum amount is called the solubility. of the solute. It is usually expressed in terms of the amount of solute that can dissolve in 100 g of the solvent at a given temperature. Is the maximum amount of solvent dissolved in a solvent?2.3. Solubility is defined as the maximum amount of a substance that will dissolve in a given amount of solvent at a specified temperature. What is the maximum amount of solute dissolved?A saturated solution is a solution that contains the maximum amount of solute that is capable of being dissolved. How much solute can be dissolved in a given amount of solvent?Answers. Solubility is the amount of a solute that can dissolve in a given amount of solute, typically 100 mL. The solubility of solutes varies widely. What is the maximum amount of solute that will dissolve in a given quantity of solvent at a given temperature and pressure?The maximum amount of a solute that can dissolve in a solvent at a specified temperature and pressure is its solubility. Is it possible to dissolve more than maximum amount of solute?Sometimes, a solution contains more dissolved solute than is normally possible. This type of solution is said to be supersaturated. A saturated solution can become supersaturated if more solute is added while the temperature is raised. Then if this solution is slowly cooled, the solute can remain dissolved. When a solution has more solute than it can hold is called?Saturated solutions have dissolved the maximum amount of solute possible at a given temperature. This is defines the solubility of the solute in the solvent. Supersaturated solutions contain more solute than is present in a saturated solution. What are the 5 factors affecting solubility?
Which two liquids will dissolve in each other?When two liquids can be readily combined in any proportions, they are said to be miscible. An example would be alcohol and water. Either of the two can totally dissolve each other in any proportion. Two liquids are defined as immiscible if they will not form a solution, such as oil and water. Which solid is insoluble in all three solvents?(c) Chalk is insoluble in all the three solvents. Butter is an example of colloidal solution in which liquid is dispersed in solid. It is also called gel. How can you increase the amount of solute dissolved in a solvent?temperature — For liquids and solid solutes, increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute will dissolve. For gases, the reverse is true. An increase in temperature decreases both solubility and rate of solution. What is the solubility of KCl at 40 C in 100 grams of water?The solubility of KCl at 40 degrees Celsius is 39 g in 100 g of water. What is the general term for a solute dissolved in a solvent?
What is a solution containing all of the solute that a solvent can dissolve at a certain temperature and pressure?
What is the most convenient method to express the concentration of solutions?Molality is the most convenient method to express the concentration of solutions because it involves the mass of liquids rather than their volumes. Why does crushing a solid increase the speed at which the solid dissolves?Why does crushing a solid increase the speed at which a solid dissolves? Crushing increases the amount of contact between the solute and the solvent. |
What is the solution that contains the maximum amount of solute dissolved by a given amount of solvent?
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