What is hard water and what are the effects of it?

Answer 1

All of the water we use in our homes passes through what is called the "Water Cycle"* that you learned about in grade school. Water moves from the earth to the atmosphere and back again in a continuous cycle. The Sun evaporates surface water from lakes and rivers and the land itself. It rises as invisible water vapour. When it binds with dust particles, the result is clouds.

As the atmospheric temperature changes, the water vapour condenses and falls as precipitation. It combines with gases like carbon dioxide as it falls, becoming mildly acidic. Once on the ground it seeps through soil and rock where the acidity causes the water to absorb various minerals that contribute to its hardness. The most common are calcium and magnesium, though the list also includes iron, aluminum, and manganese.

There are several systems for measuring the water hardness. Water is considered hard if it has 120 to 180 milligrams of calcium per litre (mg/L). Soft water has 17.1 milligrams per litre. Since the hardness of your water depends on the local geology, there are variations in different parts of Canada. In Toronto, for example, the water has 121 mg/L of dissolved calcium thus falling into the "hard" category, whereas in Winnipeg, the figure is 77 mg/L or "moderately hard."

Hard water causes calcium deposits on tubs and tiles, Plumbing and appliances. This means cleaning your bathroom is more work and appliances that use hard water have a shorter life. Hard water requires more

soap to clean effectively and also leaves a residue on everything from glassware, to clothing to your skin. The dissolved minerals also negatively impact the taste of your drinking water and everything you make with it or cook in it. Many companies offer free water testing to determine if you have hard water in your home.

The optimum solution to hard water is to install a whole house water treatment system.

Sources: rainsoftdirect.com/homewatertest.php, http://watersoftener.wordpress.com/

The term "hard water" is used to describe water that has a high mineral content, usually calcium and magnesium in the form of carbonates, but may include several other metals as well as bicarbonates and sulfates, (water with a low mineral content is known as soft water).

A high enough concentration of these metals in your water can cause white lime scales on surfaces which the water comes into contact with. Total water 'hardness' is reported as ppm w/v (or mg/L) of calcium carbonate (CaCO3).

Water hardness usually measures the total concentration of calcium and magnesium, the two most common metal ions, although in some locations around the world iron, aluminum, and manganese may also be present at elevated levels. Calcium usually enters the water as either calcium carbonate (CaCO3), from limestone or chalk, or from mineral deposits of calcium sulfate (CaSO4).

Answer 2

What is known as the hardness of water?

As water from wells, rivers and reservoirs has been reached after percolating through soil and rocks, it does contain substances from the ground, which have been dissolved.The hardness of water mainly depends on the Calcium(II) and Magnesium(II) ion concentrations of the specific source. The hardness is classified approximately as at below Calcium(II) and Magnesium(II) ion concentrations;

• Soft water contains lesser than 57 mg dm-3
• Moderately hard water contains between 57 mg dm-3 and 100 mg dm-3
• Hard water contains between 100 mg dm-3 and 143 mg dm-3
• Very hard water contains more than 143 mg dm-3

These are present when rain water which is faintly acidic due to dissolved carbon dioxide, and has percolated through rocks made of limestone, which have Calcium(II) and/or Magnesium(II) ions.

H2O(l) + CaCO3(s) --> CaCO3(aq) [direct dissolving]

H2O(l) + CaCO3(s) + CO2(g) --> Ca(HCO3)2(aq)

Effects of hard water

These reactions are reversed when heating, and solid carbonates do deposit in kettles, hot water pipes etc. which would reduce the efficiency of heating and may cause blockages respectively. There are two types of hardness in water.

• Temporary hardness caused by Calcium(II) and Magnesium(II) hydrogen-carbonates which can be removed by a process of heating and it gives a lesser impact.
• Permanent hardness caused by Calcium(II) and Magnesium(II) carbonates which cannot be removed by a process of heating and it gives a higher impact.

When soap is used with hard water, a scum is formed and it;

• Makes the need of excess soap for the process of cleaning.
• Might damage the fabric.

A reaction involved in forming the scum is given below.

2 C17H35CO2-Na+(aq) + Ca2+(aq) --> Ca(C17H35CO2)2(s) + 2 Na2+(aq)