Final answer:
To soften hard water, one can use ion exchange to replace hard minerals with sodium ions, lime softening to precipitate out calcium and magnesium, and commercial water softeners or builders which use ion-exchange resins and sequestering agents.
Step-by-step explanation:
There are several methods to soften hard water, each with its distinct mechanisms and benefits. Here are three common ways:
- Ion Exchange: This process involves exchanging unwanted ions, such as calcium (Ca2+) and magnesium (Mg2+), with more preferable ions like sodium (Na+). Hard water passes through a resin that traps the unwanted ions and releases sodium ions back into the water.
- Lime Softening: In this method, calcium hydroxide (Ca(OH)2), also known as slaked lime, is added to the water. The lime reacts with the calcium and magnesium in the water and causes them to precipitate out, which can be filtered from the water.
- Commercial Water Softeners and Builders: These systems often use ion-exchange resins with a sodium salt complexing agent. The hard water passes over the resin, swapping calcium and magnesium ions with sodium. Builders can also act as water softeners by using sequestering agents to remove hard water ions.