The diminished ability of soap to lather is not only annoying, but can also be potentially harmful economically. Businesses that depend on the foaming of soap, such as car washes and pet groomers, may wish to soften hard water to avoid excessive use of soap due to a decreased ability to lather. Likewise, it is often necessary to soften water that comes into contact with pipes to avoid the destructive and compromising build-up of deposits.
Also, many people may find the calcifying effects that hard water has on faucets and other items unfavorable and choose to soften the water to prevent such mineral deposits from forming. Still others may dislike the sticky, dry feeling left by the precipitation of soap scum onto the skin.
Whatever the reasons, there are many processes available to soften hard water. One way to soften water is through a process called ion exchange. During ion exchange, the unwanted ions are "exchanged" for more acceptable ions.
To do this, the hard water is conducted through a zeolite or resin-containing column, which binds the unwanted ions to its surface and releases the more tolerable ions.
In this process, the hard water ions become "fixed" ions because of their attachment to the resin material. This process is illustrated in Figure 1. Unfortunately, this process has the disadvantage of increasing the sodium content of drinking water, which could be potentially hazardous to the health of people with sodium-restricted diets.
Another process is called lime softening. In this process, the compound calcium hydroxide, Ca OH 2 , is added to the hard water. The calcium hydroxide, or "slaked lime," raises the pH of the water and causes the calcium and magnesium to precipitate into CaCO 3 and Mg OH 2. These precipitates can then be easily filtered out due to their insolubility in water, shown below by the small solubility constant of magnesium hydroxide the solubility product constant for calcium carbonate is shown above.
After precipitation and removal of the offending ions, acid is added to bring the pH of the water back to normal. Chelating agents can also be used to soften hard water. Polydentate ligands, such as the popular hexadentate ligand EDTA, bind the undesirable ions in hard water.
These ligands are especially helpful in binding the magnesium and calcium cations, which as already mentioned are highly prevalent in hard water solutions.
The chelating agent forms a very stable ring complex with the metal cations, which prevents them from interacting with any other substances that may be introduced to the solution, such as soap. In this way, chelators are able to diminish the negative effects associated with hard water. The large value of the formation constant K f reflects the tendency of the reaction to proceed to completion in the forward direction.
The final process, reverse osmosis, uses high pressures to force the water through a semipermeable membrane. This membrane is generally intended to be impermeable to anything other than water.
The membrane serves to filter out the larger ions and molecules responsible for the water's hardness, resulting in softened water. During this process, the water is forced from an area with a high concentration of solute in the form of dissolved metal ions and similar compounds, to an area that is very low in the concentration of these substances. In other words, the water moves from a state of hardness to a softer composition as the ions causing the water's hardness are prevented passage through the membrane.
Reverse Osmosis does have a disadvantage of wasting wastewater compared to other water treatment methods. This process is shown in Figure 2 below. Note that this figure describes the desalination of salt water. However, the process for softening hard water is the same. Hardness of water is usually attributed to calcium and magnesium salts but any cation with two or more charges can cause it eg iron II here. The cation will form a precipitate scum with soap, eg:.
This scum wastes soap and can cause abrasion to clothes, as well as causing unsightly deposits round baths and showers. This collection of over practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Demonstrate the movement of positive and negative ions with a simpler, safer version of this classic demo.
Meet Brent Murray, a food scientist with a passion for beer, ice cream, clotted cream and other food colloids. Use this practical to investigate how solutions of the halogens inhibit the growth of bacteria and which is most effective. Site powered by Webvision Cloud. Skip to main content Skip to navigation. No comments. This experiment should take about 30 minutes.
Wear eye protection throughout. Genuine liquid soap or soap flakes from which the liquid can be made, are increasingly difficult to obtain. Lux soap flakes are ideal for making liquid soap if you can source them. They do not form a stable emulsion and precipitate out overnight. Note that most liquid hand washes are based on the same detergents as washing-up liquids and do not contain soap. To obtain soap solution from soap flakes, dissolve soap flakes or shavings from a bar of soap in ethanol — use IDA Industrial Denatured Alcohol.
Do not dissolve in water. Procedure Set up eight labelled test tubes, each containing 1 cm depth of one of the following: distilled or deionised water sodium chloride solution calcium chloride solution magnesium chloride solution potassium nitrate solution sodium sulfate solution iron II sulfate solution magnesium sulfate solution Collect about 50 cm 3 of soap solution in a small beaker.
Hard water is formed when water percolates through deposits of calcium and magnesium-containing minerals such as limestone, chalk and dolomite. Soft water is surface water that contains low concentrations of ions and in particular is low in ions of Calcium and Magnesium. Soft water naturally occurs where rainfall and the drainage basin of rivers are formed. Home Services Water supply Water hardness. Water hardness Water's hardness is determined by the concentration of multivalent cations in the water.
Water hardness in water systems managed by Infrastruktura Bled d. Useful links: Infrastruktura Bled d.
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