Analysis of Water Hardness Objectives To learn about water hardness: how it is c

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Analysis of Water Hardness Objectives To learn about water hardness: how it is caused and how it affects everyday life To determine the hardness of an unknown water sample using volumetric analysis (titration) To identify the hardness classification of Fairfax County Water e Introduction Hardness of water or "hard water" refers to the presence of specific minerals in the water. These minerals consume soap and cause scaling in water heaters and boilers. The word 'hard' comes from the difficulty of using soap to clean clothes in water which has high concentration of minerals. In hard water, soap combines with the minerals to form a precipitate. This decreases the cleaning effectiveness of soap and forms soap scum. Adding more soap to clean the clothes simply results in more scum being produced. The minerals that contribute to water hardness -also known as "hardening ions" are usually divalent cations such as calcium, magnesium, iron, manganese and zinc cations. Since Ca2+ and Mg2+ are the most common divalent cations in surface water and groundwater, hardness is generally considered to be caused primarily by Ca and Mg Carbon dioxide dissoloved in rain water makes the rainwater slightly acidic. As this water moves through soil and rock minerals are dissolved. Because of the relatively large natural abundance of limestone deposits and other calcium minerals such as gypsum, CaSO42H2O, Ca (and Mg2") is a major component of the dissolved solids in hard water. Soaps are water-soluble sodium salts of fatty acids such as sodium stearate C17H3sCO2Na (figure I). Typically the nonpolar end of the soap binds to grease while the ionic end binds to water. When clothing is washed with soap, the water attracts the soap via the ionic end which will have dirt an comes into contact with water containing Ca2, it forms a precipitate (scum), (Ci7HssCO)2Ca, and becomes unavailable to conduct the cleaning for which it was intended (igure 2). d grease attracted at the nonpolar end. However, when soap 0 Figure I: Soap, sodium stearate. Nonpolar tail-end binds to grease and ionic head-end binds to water 0 0 Figure 2: Calcium stearate formed as a precipitate when soap comes into contact with Ca (soap scum) Although hard water is a burden on many everyday items such as cleaning agents, kettles, pipes and heaters, it has not been found to be a health hazard. In fact, the presence of Ca2 and Mg2 in hard water can be considered a dietary supplement. In this experiment, the hardening ion concentration of a sample of water is tested using a titration method to determine the hardness classification of the water sample. Experiment: Analysis of Water Hardness (Edited Oct17) 1

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Analysis of Water Hardness Objectives To learn about water hardness: how it is c

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