|
|
Hard water is a label commonly used to describe water that has a significant concentration of dissolved metal ions. Hard water can leave a film on your skin after a shower because soaps and oils do not lather and rinse as easily. Magnesium and calcium are two offending species in creating hard water. Iron, Fe2+ and manganese, Mn2+ also cause problems. Iron can stain clothes, and dissolved minerals build up on water pipes. 
|
|
|
The process of"water softening" uses substances that precipitate dissolved minerals. Many rural water treatment plants add hydroxide, OH− and carbonate, CO32− to the water supply. These ions react with Mg2+ and Ca2+ ions to form insoluble precipitates. For example, Mg2+ reacts with carbonate, CO32− in a water treatment holding tank. The MgCO3(s) precipitate that forms settles to the bottom of the holding tank where it is easily removed by filtering.
|
|
Hard water can affect your plumbing by precipitating out some calcium carbonate. These precipitates, called pipe scaling, can be removed (descaled) with a dilute acid which creates another double replacement reaction that dissolves the scale into soluble compounds, water and gas. For example, when solid magnesium carbonate, MgCO3, and hydrochloric acid, HCl, are mixed, Mg2+ and H+ ions exchange places resulting in soluble magnesium chloride, MgCl2 , H2O, and carbon dioxide gas, CO2, that just bubbles away.
|
|
What reaction occurs when a solution of copper(II) nitrate (Cu(NO3)2) is combined with a solution of potassium chloride (KCl)? Write the complete balanced reaction including reactant and product states.
|
| Asked |
Write a reaction between Cu(NO3)2 and KCl, and identify states. |
| Given |
Formulas for both reactant solutions. |
| Relationships |
Because both reactants are solutions, both are aqueous. Both reactants are ionic compounds so a double replacement reaction will occur. The solubility rules state K+, a group 1 metal ion, and nitrates are soluble. Copper is not listed as one of the insoluble chlorides, so it is soluble. |
| Solve |
Cu(NO3)2(aq) + 2KCl(aq) → CuCl2(aq) + 2KNO3(aq) |
| Answer |
According to the solubility table, potassium nitrate is soluble and dissociates to K+(aq) and NO3-(aq). CuCl2 is also soluble and exists as dissociated Cu2+ and Cl− ions in solution. All ions are balanced.
|
|
| |
|
