Hard water完成

nullHard water Hard water ZhouHaibinnullHard water is water that has high mineral content (in contrast with soft water). Hardness refers to the concentration of calcium and magnesium in water.Sources of hardness Sources of hardness Natural source = rocks Limestone(石灰岩) = hard water The following reaction describes the dissolving/formation of calcium carbonate scales: CaCO3 + CO2 + H2O ⇋ Ca2+ + 2HCO3- Effects of hard water Effects of hard water Hard water is generally not harmful to one’s health but can pose serious problems in industrial settings。 When heated, the carbonates precipitate(沉淀物) out of solution. null In addition to narrowing the pipes, scale prevents efficient heat transfer(传热), so a water heated with scale(生水垢) will have to use a lot of energy.Soft water can be a problemSoft water can be a problemin soft water, heavy metals are more poisonous, drinking it over long time can increase chance of heart attack. 0 – 60 = soft water 61-120 = moderately(适度) hard water 121-180 = hard water 181+ = very hard water Hardness and alkalinity are related（有关系） Measurement Measurement Hardness can be quantified by instrumental analysis. The total includs both Ca2+ and Mg2+ ions, is reported in parts per million (ppm) or weight /volume (mg/L) of calcium carbonate (CaCO3) in the water. water softeners water softeners Hard water can be softened by treating it with lime(石灰) or by passing it over an ion exchange resin(离子交换树脂). Water flows over the resin surface, the cations stick to the resin and the hydrogen and hydroxide that are released combine to form pure water. nullVery hard water will end up tasting saltier than soft water. Rainwater and distilled water are soft, because they contain few ions. Thank you!!!Thank you!!!