Apr 03, †Ј When a solution is formed, it is characterized by four main properties, known as colligative properties: vapor pressure, boiling point, freezing point and osmotic pressure. Solutes added to a solvent create a solution that is different from the original solvent. Mar 20, †Ј In all solutions, whether gaseous, liquid, or solid, the substance present in the greatest amount is the solvent, and the substance or substances present in lesser amounts are the solute (s). The solute does not have to be in the same physical state as the solvent, but the physical state of the solvent usually determines the state of the solution. As long as the solute and solvent combine to give a homogeneous solution, the solute is said to be soluble in the solvent.
Solutions are likely to have properties similar to those of their major componentЧusually the solvent. However, some what timezone is oklahoma city in properties differ significantly from those of the solvent. Here, we will focus on liquid solutions that have a solid solute, but many of the effects we will discuss in this section are applicable to all solutions.
Solutes affect some properties of solutions that depend only on the concentration of the dissolved particles. These properties are called colligative properties. Four important colligative properties that we will examine here are vapor pressure depression, boiling point elevation, freezing point depression, and osmotic pressure.
Molecular compounds separate into individual molecules when they are dissolved, so for every 1 mol of molecules dissolved, we get 1 mol of particles. In contrast, ionic compounds separate into their constituent ions when they dissolve, so 1 mol of an ionic compound will produce more than 1 mol of dissolved particles. All liquids evaporate. In fact, given enough volume, a liquid will turn completely into a vapor. If enough volume is not present, a liquid will evaporate only to the point where the rate of evaporation equals the rate of vapor condensing back into a liquid.
The pressure of the vapor at this point is called the vapor pressure of the liquid. The presence of a dissolved solid lowers the characteristic vapor pressure of a liquid so that it evaporates more slowly. The exceptions to this statement are if the solute itself is a liquid or a gas, in which case the solute will also contribute something to the evaporation process.
We will not discuss such solutions here. A related property of solutions is that their boiling points are higher than the boiling point of the pure solvent. Because the presence of solute particles decreases the vapor pressure of the liquid solvent, a higher temperature is needed to reach the boiling point.
This phenomenon is called boiling point elevation. For every mole of particles dissolved in a liter of water, the boiling point of water increases by about 0. The addition of one mole of sucrose molecular compound in one liter of water will raise the boiling point from 0 C to Furthermore, the addition of one mole of CaCl 2 in one liter of water will raise the boiling point by 3 x 0.
Some people argue that putting a pinch or two of salt in water used to cook spaghetti or other pasta makes a solution that has a higher boiling point, so the pasta cooks faster. In actuality, the amount of solute is so small that the boiling point of the water is practically unchanged. The presence of solute particles has the opposite effect on the freezing point of a solution.
When a solution freezes, only the solvent particles come together to form a solid phase, and the presence of solute particles interferes with that process.
Therefore, for the liquid solvent to freeze, more energy must be removed from the solution, which lowers the temperature. Thus, solutions have lower freezing points than pure solvents do. This phenomenon is called freezing point depression. For every mole of particles in a liter of water, the freezing point decreases by about 1. Both boiling point elevation and freezing point depression have practical uses. This is because the solution made by dissolving sodium chloride or calcium chloride in water has a lower freezing point than pure water, so the formation of ice is inhibited.
Colligative properties depend on the number of dissolved particles, so the solution with the greater number of particles in solution will show the greatest deviation.
The boiling point increases 0. For this estimation, let's assume that 1 liter of solution is roughly the same volume as 1 liter of water. Each CaCl 2 unit separates into three ions. The normal boiling point of water is 0 C, so the boiling point of the solution is raised to The last colligative property of solutions we will consider is a very important one for biological systems.
It involves osmosisthe process by which solvent molecules can pass through certain membranes but solute particles cannot. When two solutions of different concentration are present on either side of these membranes called semipermeable membranesthere is a tendency for solvent molecules to move from the more dilute solution to the more concentrated solution until the concentrations of the two solutions are equal.
This tendency is called osmotic pressure. External pressure can be exerted on a solution to counter the flow of solvent; the pressure required to halt the osmosis of a solvent is equal to the osmotic pressure of the how to get drug money. Osmolarity osmol is a way of reporting the total number of particles in a solution to determine osmotic pressure. It is defined as the molarity of a solute times the number of particles a how long do you have to keep your taxes unit of the solute makes when it dissolves represented by i :.
If more than one solute is present in a solution, the individual osmolarities are additive to get the total osmolarity of the solution. Solutions that have the same osmolarity what are the three properties of a solution the same osmotic pressure. If solutions of differing osmolarities are present on opposite sides of a semipermeable what is the price of scientific calculator, solvent will transfer from the lower-osmolarity solution to the higher-osmolarity solution.
Counterpressure exerted on the high-osmolarity solution will reduce or halt the solvent transfer. An even higher pressure can be exerted to force solvent from the high-osmolarity solution to the low-osmolarity solution, a process called reverse osmosis.
Reverse osmosis is used to make potable water from saltwater where sources of fresh water are scarce. Determine the osmolarity of each solution and predict the direction of solvent flow. The solvent will flow into the solution of higher osmolarity. The main function of the kidneys is to filter the blood to remove wastes and extra water, which are then expelled from the body as urine. Some diseases rob the kidneys of their ability to perform this function, causing a buildup of waste materials in the bloodstream.
If a kidney transplant is not available or desirable, a procedure called dialysis can be used to remove waste materials and excess water from the blood. A section of tubing composed of a semipermeable membrane is immersed in a solution of sterile water, glucose, amino acids, and certain electrolytes. The osmotic pressure of the blood forces waste molecules and excess water through the membrane into the sterile solution. Red and white blood cells are too large to pass through the membrane, so they remain in the blood.
After being cleansed in this way, the blood is returned to the body. Dialysis is a continuous process, as the osmosis of waste materials and excess water takes time. Typically, 5Ч10 lb of waste-containing fluid is removed in each dialysis session, which can last 2Ч8 hours and must be performed several times a week.
Although some patients have been on dialysis for 30 or more years, dialysis is always a temporary solution because waste materials are constantly building up in the bloodstream. A more permanent solution is a kidney transplant.
If solutions of different osmolarity exist on either side of the cells, solvent water may pass into or out of the cells, sometimes with disastrous results. Consider what happens if red blood cells are placed in a hypotonic solution, meaning a solution of lower osmolarity than the liquid inside the cells. The cells swell up as water enters them, disrupting cellular activity and eventually causing the cells to burst. This process is called hemolysis. What channel is the all star race on dish network red blood cells are placed in a hypertonic solution, meaning one having a higher osmolarity than exists what are the three properties of a solution the cells, water leaves the cells to dilute the external solution, and the red blood cells shrivel and die.
This process is called crenation. Only if red blood cells are placed in isotonic solutions that have the same osmolarity as exists inside the cells are they unaffected by negative effects of osmotic pressure. Glucose solutions of about 0. The concentration of an isotonic sodium chloride NaCl solution is only half that of an isotonic glucose C 6 H 12 O 6 solution because NaCl produces two ions when a formula unit dissolves, while molecular C 6 H 12 O 6 produces only one particle when a formula unit dissolves.
The osmolarities are therefore the same even though the concentrations of the two solutions are different. Osmotic pressure explains why you should not drink seawater if you are abandoned in a life raft in the middle of the ocean. Its osmolarity is about three times higher than most bodily fluids. You would actually become thirstier as water from your cells was drawn out to dilute the salty ocean water you ingested.
Our bodies do a better job coping with hypotonic solutions than with hypertonic ones. The excess water is collected by our kidneys and excreted. Osmotic pressure effects are used in the food industry to make pickles from cucumbers and other vegetables and in brining meat to make corned beef.
It is also a factor in the mechanism of getting water from the roots to the tops of trees! The use of perfusionists has grown rapidly since the advent of open-heart surgery in Most perfusionists work in operating rooms, where their main responsibility is to operate heart-lung machines. During many heart surgeries, the heart itself must be stopped.
In these situations, a heart-lung machine keeps the patient alive by aerating the blood with oxygen and removing carbon dioxide. The perfusionist monitors both the machine and the status of the blood, notifying the surgeon and the anesthetist of any concerns and taking corrective action if the status of the blood becomes abnormal.
Despite the narrow parameters of their specialty, perfusionists must be highly trained. Certified perfusion education programs require a student to learn anatomy, physiology, pathology, chemistry, pharmacology, math, and physics. A college degree is usually required. Some perfusionists work with other external artificial organs, such as hemodialysis machines and artificial livers.
Explain how the following properties of solutions differ from those of the pure solvent: vapor pressure, boiling how to send an ecard via text message, freezing point, and osmotic pressure. Colligative properties are characteristics that a solution has that depend on the number, not the identity, of solute particles.
In solutions, the vapor pressure is lower, the boiling point is higher, the freezing point is lower, and the osmotic pressure is higher. Estimate the boiling point of each aqueous solution. The boiling point how to scan from a brother printer pure water is Estimate the freezing point of each aqueous solution.
The freezing point of pure water is 0. Explain why salt NaCl is spread on roads and sidewalks to inhibit ice formation in cold weather. Salt NaCl and calcium chloride CaCl 2 are used widely in some areas to minimize the formation of ice on sidewalks and roads. One of these ionic compounds is better, mole for mole, at inhibiting ice formation. Which is that likely to be?
Answers Colligative properties are characteristics that a solution has that depend on the number, not the identity, of solute In solutions, the vapor pressure is lower, the boiling point is higher, the freezing point is lower, and the osmotic. A solution is a homogeneous mixture of two or more substances. A solution has a solvent and a solute as its components. The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent. In order to form a solution, the solute must be surrounded, or solvated, by the solvent. Solutes successfully dissolve into solvents when solute-solvent bonds are stronger than either solute-solute bonds or solvent-solvent bonds. Qualitatively, one can determine the solubility of a solute in a solvent by using the rule Уlike dissolves likeФ.
To form a solution, molecules of solute and solvent must be more attracted to each other than themselves. The strength of the intermolecular forces between solutes and solvents determines the solubility of a given solute in a given solvent.
In order to form a solution, the solute must be surrounded, or solvated, by the solvent. Solutes successfully dissolve into solvents when solute-solvent bonds are stronger than either solute-solute bonds or solvent-solvent bonds.
In general, solutes whose polarity matches that of the solvent will generally be soluble. For example, table salt NaCl dissolves easily into water H 2 O because both molecules are polar. There are two conceptual steps to form a solution, each corresponding to one of the two opposing forces that dictate solubility. If the solute is a solid or liquid, it must first be dispersed Ч that is, its molecular units must be pulled apart.
This requires energy, and so this step always works against solution formation always endothermic, or requires that energy be put into the system. Step 1 of dissolution : Molecules going from an ordered state, such as a solid, to a disordered state require an input of energy.
The nature of the solute X and solvent Y determines whether dissolution is energetically favorable or unfavorable. If the solute binds to other solute X-X bond more strongly than the solute binds to the solvent X-Y bond , then the dissolution is not energetically favorable. In this case, the potential energy is lower when the solute and solvent can form bonds. If the X-Y attractions are stronger than the X-X or Y-Y attractions, the dissolution reaction is exothermic and releases energy when the solute and solvent are combined.
Since the dissolution of the solvent X-X and solute Y-Y is always positive, the determining factor for solution formation is the value of X-Y. Remember that the interactions between X and Y, represented above as X-Y, are classified as intermolecular forces, which are not covalent bonding interactions. After dissolution occurs, solvation follows. If solvation releases more energy than is consumed during dissolute, then solution formation is favored and the solute is soluble in the solvent.
Many intermolecular forces can contribute to solvation, including hydrogen bonding, dipole-dipole forces, and Van Der Waals forces. Another common example of these forces at work is an ion-dipole interaction, which arises when water solvates ions in solution.
This interaction arises most prevalently when strong or weak electrolytes are place in water. Consider the dissolution of table salt sodium chloride in water:. Solvation of a cation by water. In this case, the anion Cl Ч is solvated by the positive dipoles of water, which are represented by hyrogen atoms. These interactions explain why most ionic compounds are considered soluble in water, unless specifically labeled otherwise.
An increase in entropy occurs when a solution is formed, providing one of the many driving forces for this process. As anyone who has shuffled a deck of cards knows, disordered arrangements of objects are statistically more favored, simply because there are more ways in which they can be realized. The more the number of objects increases, the more statistics governs their most likely arrangements.
Chemistry deals with a huge number of objects molecules , and their tendency to become as spread out and disordered as possible can become overwhelming. However, when they become spread out and disordered, the thermal energy they carry with them is also dispersed; the availability of this energy as measured by the temperature is also of importance.
Entropy is indeed a fascinating, but somewhat confusing, topic. In fact, it is so important that the topic of entropy deals with two of the three laws of thermodynamics.
Order and disorder : This image shows a series of blue and green squares going from a state of disorder randomness to a state of order a clear repeating pattern. In this example, that is to say, entropy decreases and opposes the transition. This term increases with increasing temperature. In a similar manner entropy plays an important role in solution formation. Entropy commonly increases especially for ions as they transition from molecule to ions.
This is because we are essentially increasing the number of particles from one compound to two or more depending upon the composition.
Consider, the dissolution of sodium sulfate,. All these factors increase the entropy of the solute. This factor can sometimes lead to only a small increase in entropy although a large increase is expected. Thus, in the very common case in which a small quantity of solid or liquid dissolves in a much larger volume of solvent, the solute becomes more spread out in space, and the number of equivalent ways in which the solute can be distributed within this volume is greatly increased.
This is the same as saying that the entropy of the solute increases. Think of entropy in solution formation by picturing the addition of food coloring to pure water. Upon first addition of the food coloring, the dye molecules are concentrated near their contact point. As time proceeds, these molecules of dye are dispersed more uniformly throughout the solution even without mixing. Since the H solution for this process is approximately zero an ideal solution , the only thermodynamic factor driving the mixing is the entropy term.
This formation of solution increases entropy as the molecules become more evenly distributed and ordered through the process of diffusion. If the energetics of dissolution are favorable, this increase in entropy means that the conditions for solubility will always be met.
Even if the energetics are slightly endothermic, the entropy effect can still allow the solution to form, although they may perhaps limit the maximum concentration that can be achieved. Predict whether a given ionic solid will dissolve in water given the lattice energy and heat of hydration. Solubility depends on dissolution of the solute into the solvent and, like all chemical reactions, is governed by the laws of thermodynamics. In order for any chemical reaction to proceed, it must be thermodynamically favorable.
Many factors influence how thermodynamically favorable a given reaction is, including the heat of hydration, or hydration energy released when water solvates, or surrounds, an ion, and the amount of energy required to overcome the attractive forces between solute molecules, known as lattice energy. Since the coulombic forces that bind ions and highly polar molecules into solids are quite strong, we might expect these solids to be insoluble in most solvents.
The attractive interactions between ionic molecules are called the lattice energy, and they must be overcome for a solution to form. Ionic solids are insoluble in the majority of non-aqueous solvents, but they tend to have high solubility specifically in water. The key factor that determines solubility is the interaction of the ions with the solvent.
The electrically-charged ions undergo ion- dipole interactions with water to overcome strong coulombic attraction, and this produces an aqueous solution. The water molecule is polar; it has a partial positive charge on the hydrogens while oxygen bears a partial negative charge. This dipole arises from the disparity in electronegativity present in the O-H bonds within the water molecule.
Furthermore, the two lone pairs on the oxygen in water also contribute to the stabilization of any positively charged ions in solution. As a consequence, ions in aqueous solutions are always hydrated; that is, they are quite tightly bound to water molecules through ion-dipole interactions. The number of water molecules contained in the primary hydration shell, which completely encompasses the ion, varies with the radius and charge of the ion.
The first reaction ionization is always endothermic; it takes a lot of work to break up an ionic crystal lattice into its component ions. Lattice energy is defined as the energy that is released when one mole of ionic solid is formed from gaseous ions, and it increases with increasing atomic charge and decreasing atomic size radii.
In fact, some compounds are strictly insoluble due to their high lattice energies that cannot be overcome to form a solution. From this relationship, we can clearly see that the processes of overcoming the lattice energy and hydrating the ions are in competition with one another.
The value of H solution is dependent upon the magnitudes of H hydration and H lattice energy of the solute. Favorable conditions for solution formation typically involve a negative value of H solution ; this arises because the hydration process exceeds the lattice energy in the solute.
As often happens for a quantity that is the sum of two large terms having opposite signs, the overall dissolution process can be either endothermic or exothermic. H solution is just one of the factors determining solution formation, but it is typically the major consideration in solution formation because of the role that enthalpy plays in most thermodynamic considerations.
The average time an ion spends in a hydration shell is about two to four nanoseconds, which is about two orders of magnitude longer than the lifetime of an individual H 2 OЧH 2 O hydrogen bond. The relative strengths of these two intermolecular forces is apparent: ion-dipole interactions are stronger than hydrogen bond interactions.
A hot solution results when the heat of hydration is much greater than the lattice energy of the solute. Enthalpy diagram for the dissolution process : The enthalpy diagram showing exothermic solution formation.
The second conceptual step is solvation, which corresponds to the force of the solute-solvent intermolecular attraction that needs to be formed in order to form a solution. Many intermolecular forces can contribute to solvation, including hydrogen bonding, dipole -dipole forces, Van Der Waals forces, and ion -dipole interactions.
Key Terms intermolecular forces : attractive and repulsive forces between molecules. Solutions and Entropy Changes An increase in entropy occurs when a solution is formed, providing one of the many driving forces for this process.
Learning Objectives Recall that entropy favors dissolution because the potential for randomness is increased. Key Takeaways Key Points Entropy can be thought of as the randomness or spread-outedness of a group of molecules. Increasing randomness is favorable. There is an entropy change associated with the formation of a solution, an increase in entropy randomness that thermodynamically favors the solution over the two original states.
If the other energetics of dissolution are favorable, this increase in entropy means that the conditions for solubility will always be met. Even if the energetics are slightly endothermic the entropy effect can still allow the solution to form.
Key Takeaways Key Points In order to dissolve an ionic solid, water molecules must break up the interactions between all of the ions in the solid. To do this, they orient themselves such that they effectively reduce the localized charge on the ions. This is called hydration. Hydration of ions is a thermodynamically favorable process, and as such can release heat. Key Terms thermodynamics : The science of the conversions between heat and other forms of energy. The more the ion is hydrated, the more heat is released.