File Name: temporary hardness and permanent hardness of water .zip
School Chemistry Notes: Explaining hard and soft water. The difference between hard water and soft water is explained and the causes and treatment of hard water fully explained.
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School Chemistry Notes: Explaining hard and soft water. The difference between hard water and soft water is explained and the causes and treatment of hard water fully explained. Extra Aqueous Chemistry Index:. Water cycle, potable water, water treatment, pollution, tests for ions. Colloids — sols, foam and emulsions. Gas and salt solubility in water and solubility curves. Calculation of water of crystallisation.
Hard and Soft Water. Its not a very accurate titration. This method of determining hardness involves a soap titration. You fill the burette 10 cm 3 or 50 cm 3 capacity, depending on how big the titrations are and level of the reading to 0.
The bottom of the meniscus should be on the reading you take e. Measure out 50 cm 3 of an unboiled water sample into a conical flask and a rubber bung to provide a good seal.
Keep the tip of the burette down into the flask. Add the soap solution in small portions e. After each addition, put the bung on the conical flask and give the mixture a good shake for a few seconds. The titration is complete when a good soapy bubble lather is obtained that persists for at least 30 seconds. The whole procedure is repeated with 50 cm3 of the same water sample, BUT this time from the water is boiled for a few minutes before doing the soap titration.
Record all your results in a suitable table for analysis and drawing conclusions about whether the water is hard or not, AND how much of the hardness is temporary or permanent? The procedure is illustrated in the diagram above where three situations are described. Put the bung on and shake vigorously. You should get a good lather immediately. You can also consider this as a 'blank titration' and subtract it from the final titration reading.
You should not detect any hardness in pure water, but it always takes a little soap to get a good lather of soap bubbles.
This 0. Therefore all your hard water titration results should be corrected by subtracting 0. If the water contains any hardness a grey-white precipitate will form 'scum' instead of a lather, on further additions e. Eventually enough soap is added to precipitate all the hardness and a good lather will then form.
Think of the titration volumes as ' units of hardness ', arbitrary, but enables comparisons to be made between water samples as long as it involves the same standard soap solution. The boiled sample titration will often be less because boiling destroys temporary hardness. Soft water containing no magnesium or calcium ions: It should just take a small amount of soap solution e. So you can consider the 'blank titration' as 0.
Water sample D. Conclusion: A roughly equal mixture of permanent hardness and temporary hardness. Extra Notes : This method does not distinguish between hardness caused magnesium compounds and hardness caused by calcium compounds in the water. Any other apparatus you are likely to need, should be on the diagram above! Water cycle, treatment, pollution.
Website 1. Doc Brown's Chemistry. Enter chemistry words e. Water cycle, potable water, water treatment, pollution, tests for ions 2. The Determination of hardness in a sample of water How can you measure the hardness in water? Procedure for determining the hardness in water This method of determining hardness involves a soap titration. Repeat this with further portions of the soap solution. The procedure is illustrated in the diagram above where three situations are described 0.
Water sample A Soft water containing no magnesium or calcium ions: It should just take a small amount of soap solution e. Volume of soap solution cm 3 to give a good lather of soap bubbles Relative units of hardness. Doc Brown's School Chemistry Website. All copyrights reserved on revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted.
Hard water is water that has high mineral content in contrast with " soft water ". Hard water is formed when water percolates through deposits of limestone , chalk or gypsum  which are largely made up of calcium and magnesium carbonates , bicarbonates and sulfates. Iron oxides or iron carbonates can give a reddish brown colouration to hard water deposits. Hard drinking water may have moderate health benefits. It can pose critical problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers , cooling towers , and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of foam formation when soap is agitated in water, and by the formation of limescale in kettles and water heaters. Natural rainwater, snow and other forms of precipitation typically have low concentrations of multivalent cations such as Calcium and Magnesium.
Many industrial and domestic water users are concerned about the hardness of their water. Hard water requires more soap and synthetic detergents for home laundry and washing, and contributes to scaling in boilers and industrial equipment. Hardness is caused by compounds of calcium and magnesium, and by a variety of other metals.
Depending upon its behaviour towards soap solution w. For ex: Rain water ,distilled water ,demineralised water. For ex : sea water ,river water, spring water ,lake water and well water. Causes of hardness of water. Hardness of water is due to the presence of bicarbonate ,chloride and sulphate of calcium and magnesium in it.
The most basic difference between hard and soft water is that hard water reacts with soap to form solid soap scum, and soft water does not form soap scum. The formation of soap scum on your skin is the reason that soap seems easier to rinse from your body when you shower with hard water. Hardness in water is caused by the presence of calcium ions, magnesium ions, or both.
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Беккер вздохнул, взвешивая свои возможности. Где ей еще быть в субботний вечер. Проклиная судьбу, он вылез из автобуса. К клубу вела узкая аллея.
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