Significance of colligative properties in textile industry

 Colligative properties:

In chemistry, colligative properties are those properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the nature of the chemical species present. The number ratio can be related to the various units for concentration of a solution, for example, molarity, molality, normality (chemistry), etc.

Only properties which result from the dissolution of nonvolatile solute in a volatile liquid solvent are considered. They are essentially solvent properties which are changed by the presence of the solute. The solute particles displace some solvent molecules in the liquid phase and therefore reduce the concentration of solvent, so that the colligative properties are independent of the nature of the solute. 

The word colligative is derived from the Latin word colligatus meaning bound together.

 This indicates that all colligative properties have a common feature, namely that they are related only to the number of solute molecules relative to the number of solvent molecules and not to the nature of the solute. 

Colligative properties include:

• Relative lowering of vapor pressure           

• Elevation of boiling point

• Depression of freezing point                  

• Osmotic pressure

For a given solute-solvent mass ratio, all colligative properties are inversely proportional to solute molar mass.

Measurement of these for a dilute solution of a non-ionized solute such as urea or glucose in water or another solvent can lead to determinations of relative molar masses, both for small molecules and for polymers which cannot be studied by other means. Alternatively, measurements for ionized solutes can lead to an estimation of the percentage of dissociation taking place.

They are mostly studied for dilute solutions, whose behavior may be approximated as that of an ideal solution. In fact, all of the properties listed above are only colligative in the dilute limit: at higher concentrations, the freezing point depression, boiling point elevation, vapors pressure elevation or depression, and osmotic pressure are all dependent on the chemical nature of the solvent and the solute.

Importance of colligative properties And its applications:

Colligative properties change the physical properties of the original solvent. To improve the properties of the solvent required for a process, colligative properties play a major role in altering the physical properties.

Apart from molecular mass determination. The presence of a solute increases the liquid range of a solution both by raising the boiling point and lowering the freezing point. The most important application of this phenomenon is the use of an antifreeze in the radiator of an automobile. The solute is ethylene glycol, which is not only completely miscible with water but has a very low vapor pressure and nonvolatile in character. When mixed with water, it lowers the freezing point as well as raises the boiling point. During winter it protects a car by preventing the liquid in the radiator from freezing, as water alone, if it were used instead, In hot summer, the antifreeze solution also protects the radiator from boiling over.

Sodium chloride and its group 2 analogs calcium and magnesium chloride are often used to de-ice roadways and sidewalks, due to the fact that a solution of any one of these salts will have a freezing point lower than 0 °C, the freezing point of pure water. The group 2 metal salts are frequently mixed with the cheaper and more readily available sodium chloride (“rock salt”) for use on roads, since they tend to be somewhat less corrosive than the NaCl, and they provide a larger depression of the freezing point, since they dissociate to yield three particles per formula unit, rather than two particles like the sodium chloride.

Because these ionic compounds tend to hasten the corrosion of metal, they would not be a wise choice to use in antifreeze for the radiator in your car or to de-ice a plane prior to takeoff. For these applications, covalent compounds, such as ethylene or propylene glycol, are often used. The glycols used in radiator fluid not only lower the freezing point of the liquid, but they elevate the boiling point, making the fluid useful in both winter and summer. Heated glycols are often sprayed onto the surface of airplanes prior to takeoff in inclement weather in the winter to remove ice that has already formed and prevent the formation of more ice, which would be particularly dangerous if formed on the control surfaces of the aircraft

Boiling point elevation depends on the identity of the solvent and the concentration of solute particles, but not the identity of the solute. Consequently, just like freezing point depression, boiling point elevation can be used to determine the molar mass of a solute. If the solution is an electrolyte -- one containing a substance like sodium chloride, for example, which splits up when it dissolves -- this procedure becomes somewhat more complicated, because the number of particles produced by dissociation of the solute must also be taken into account. Chemists nowadays generally use techniques like mass spectrometry to determine the molar mass of compounds, but boiling point elevation and freezing point depression are still viable alternatives.

Antifreeze

Ethylene glycol or antifreeze helps prevent the water in your vehicle's radiator from freezing through freezing-point depression. But you may not have realized that it also elevates the boiling point of the fluids well. By raising the boiling point, it helps to protect against boil-overs. Many brands of antifreeze will list both the amount of boil-over protection and the freeze-up protection offered.

Cooking

Adding salt to water before or while heating it will increase its boiling point, so the water will actually be hotter than it would otherwise be when it comes to a boil. The amount of this increase, however, is quite negligible at low salt concentrations; adding a couple grams of salt to 10 cups of water, for example, would only yield a boiling point elevation of about 0.015 degrees Celsius, which will not affect your cooking significantly. Nonetheless, cooking is one use of boiling point elevation. It's also important to note that -- contrary to myth -- adding salt to water will not make it boil faster. Quite the contrary, in fact, it will take slightly longer to boil, since its boiling point has now been elevated.

Measurement of Molar Mass

Boiling point elevation depends on the identity of the solvent and the concentration of solute particles, but not the identity of the solute. Consequently, just like freezing point depression, boiling point elevation can be used to determine the molar mass of a solute. If the solution is an electrolyte -- one containing a substance like sodium chloride, for example, which splits up when it dissolves -- this procedure becomes somewhat more complicated, because the number of particles produced by dissociation of the solute must also be taken into account. Chemists nowadays generally use techniques like mass spectrometry to determine the molar mass of compounds, but boiling point elevation and freezing point depression are still viable alternatives.

Sugar Refining

Once a sugarcane crop has been harvested and the cane juice extracted, it must be refined to produce crystalline sugar for consumption. At some stages during the process, the cane juice or syrup is boiled, and the temperature at which it boils will depend on the sugar concentration. In fact, the boiling point elevation offers a way to monitor the level of saturation of the solution, which is an important consideration for crystallization

 Reverse osmosis(water purification):

RO is a water purification technology that uses a semipermeable membrane. This membrane technology is not properly a filtration method. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential, a thermodynamic parameter. Reverse osmosis can remove many types of molecules and ions from solutions, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be “selective”, this membrane should not allow large molecules or ions through the pores, but should allow smaller components of the solution to pass freely. Moreover, reverse osmosis involves a diffusive mechanism, so that separation efficiency is dependent on solute concentration, pressure, and water flux rate.

Reverse osmosis (RO) is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.

In candy making

Candy making or candy making is the preparation and cookery of candies and sugar confections. Candy making includes the preparation of many various candies, such as hard candies, jelly beans, gumdrops, taffy, liquor ice, cotton candy, chocolates and chocolate truffles, fudge, caramel candy and toffee.

Candy is made by dissolving sugar in water or milk to form a syrup, which is boiled until it reaches the desired concentration or starts to caramelize. The type of candy depends on the ingredients and how long the mixture is boiled. Candy comes in a wide variety of textures, from soft and chewy to hard and brittle. A chocolatier is a person who prepares confectionery from chocolate, and is distinct from a chocolate maker, who creates chocolate from cacao beans and other ingredients. Cotton candy is a form of spun sugar often prepared using a cotton candy machine.

In road salt:

Ice forms when the­ temperature of water reaches 32 degrees Fahrenheit (0 degrees Celsius), and that includes ice on roadways. Road salt works by lowering the freezing point of water via a process called freezing point depression. The freezing point of the water is lowered once the salt is added, so it the salt makes it more difficult for water to freeze. A 10-percent salt solution freezes at 20 degrees Fahrenheit (-6 Celsius), and a 20-percent solution freezes at 2 degrees Fahrenheit (-16 Celsius).

The key is, there has to be at least a tiny bit of water on the road for freezing point depression to work. That's why you often see trucks pre-treat roads with a brine solution (a mixture of salt and water) when ice and snow is forecast. If the roads are dry and the DOT simply puts down road salt, it likely won't make much of a difference. But pre-treating with a brine solution can help ice from ever forming, and will help reduce the amount of road salt trucks will need to spread to de-ice later.

Meat preservation:

Meats can be preserved by turning them into jerky. The meat is soaked in a very concentrated salt solution, resulting in dehydration of the meat cells. Jerky does not spoil as quickly as fresh meat, since bacteria on the surface of the salty meat will fall victim to osmosis, and shrivel up and die. This process thus extends the life of the meat without the use of refrigeration.

In hospitals:

A hospital patient receiving fluids intravenously receives an intravenous (IV) solution that is isotonic with (i.e., at the same solute concentration as) his or her cells. If the IV solution is too concentrated, osmosis will cause the cells to shrivel; too dilute a solution can cause the cells to burst. Similar problems would be experienced by freshwater fish swimming in salt water, or saltwater fish swimming in freshwater. The osmotic pressure, like other colligative properties, does not depend on the identity of the solute, but an electrolyte solute will contribute more particles per formula unit than a nonelectrolyte solute

De-icing:

Solutions freeze at lower temperatures than pure liquids. This phenomenon is exploited in “de-icing” schemes that use salt, calcium chloride, or urea to melt ice on roads and sidewalks, and in the use of ethylene glycol as an “antifreeze” in automobile radiators. Seawater freezes at a lower temperature than fresh water, and so the Arctic and Antarctic oceans remain unfrozen even at temperatures below 0 °C (as do the body fluids of fish and other cold-blooded sea animals that live in these oceans).

Kidney dialysis:

During osmosis, fluid moves from areas of high-water concentration to lower water concentration across a semi-permeable membrane until equilibrium. In dialysis, excess fluid moves from blood to the dialysate through a membrane until the fluid level is the same between blood and dialysate.

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