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Water
Causes & Removal of Hardness
Cause / Removal | Method / Equation |
---|---|
Rainwater mixes with CO2 to form weak carbonic acid (acid rain) | H20 + CO2 → H2CO3 |
Acid rain mixes with limestone to form calcium hydrogen carbonate | H2CO3 + CaCO3 → Ca(HCO3)2 |
Calcium hydrogen dissociates to form hard water (Ca2+ ions) | Ca(HCO3)2 → Ca2+ + 2HCO3- |
When boiled calcium carbonate is produced as a white precipitate | Ca(HCO3) →CaCO3 ↓ + CO2 +H2O |
Distillation | Evaporating off the water leaving dissoloved salts behind |
Using Washing Soda ( Hydrated Sodium Carbonate Na2CO3.10H2O ) | Removes hardness from water. Reacts with calcium ions: Ca2+ + CO3 2- →Caco3 ↓ |
Ion exchange | Cation exchange swaps ions that cause hardness ( Ca2+ and Mg2+) for ions that do not. Ca2= + 2RNa → R2Ca + 2Na+ *R in RNa represents resin |
Cause of Hard Water | Ca2+ and Mg2+ ions dissolved in water |
Cation Exchange | Metal ions are replaced by hydrogen ions M+ + HR → MR + H+ |
Anion Exchange | Metal ions replaced with hydroxide ions A- + ROH → RA + OH- |
Hydrogen ions and hydroxide ions combine to give water | H+ + OH- → H2O |