3. Introduction
Hardness is defined as the concentrations of calcium and magnesium
ions expressed in terms of calcium carbonate. These minerals in
water can cause some everyday problems. They react with soap and
produce a deposit called soap curd that remains on the skin and
clothes and, because it is insoluble and sticky, cannot be removed by
rinsing.
Hard water may also shorten the life of plumbing and water heaters.
When water containing calcium carbonate is heated, a hard scale is
formed that can plug pipes and coat heating elements. Scale is also a
poor heat conductor. With increased deposits on the unit, heat is not
transmitted to the water fast enough and overheating of the metal
causes failure. Build-up of deposits will also reduce the efficiency of
the heating unit, increasing the cost of fuel.
4. Objective
While hard water may have some positive aspects, such as
contributing minerals to the diet and providing a distinctive taste,
the negative aspects, including scale formation and soap
ineffectiveness, often lead to efforts to soften water for various
applications, especially in industrial and household settings.
Water softening processes can help reduce the hardness by
removing or exchanging the calcium and magnesium ions with
sodium ions.
5. Scope
1.Nutrient Source: Hard water can contribute to the intake of
essential minerals, such as calcium and magnesium, which
are important for human health. While the contribution from
hard water may be limited, it can still be a source of these
minerals.
2.Taste Preference: Some individuals prefer the taste of hard
water, finding it more flavorful than soft water. The minerals
present in hard water can give it a distinctive taste that some
people enjoy.
3.Potential Health Benefits: There is evidence suggesting
that moderate levels of calcium and magnesium in drinking
water may have potential health benefits, particularly for bone
health. However, it's essential to ensure a balanced diet to
meet nutritional needs.
6. Limitation
1.Scale Formation: One of the primary limitations of hard water is
the tendency to form scale or mineral deposits. This can lead to
the accumulation of deposits in pipes, water heaters, and other
appliances, reducing their efficiency and lifespan.
2.Soap Ineffectiveness: Hard water reacts with soap to form a
scum, reducing the soap's ability to lather and clean. This can
lead to increased soap usage and may leave a soap film on
surfaces.
3.Clogging: Mineral deposits from hard water can accumulate in
pipes, reducing water flow and potentially causing clogs. This
can result in maintenance issues and increased costs for
cleaning and repairs.
4.Laundry Issues: Hard water can affect the effectiveness of
laundry detergents and may leave mineral deposits on clothes,
reducing their lifespan and quality.
5.Appliance Damage: The scale formation in water-using
appliances, such as water heaters and dishwashers, can lead to
decreased efficiency and increased energy consumption. This
may result in higher maintenance costs and a shorter lifespan for
these appliances.
6.Cost of Water Softening: To address the limitations of hard
water, water softening systems may be required. The cost of
installing and maintaining water softeners can be a limitation for
some households and industries.
7. Principle
The principle of hard water is based on the chemical
composition and behavior of these minerals in water. Here are
the key principles:
1.Dissolution of Minerals:
1. Water percolates through rocks and soil, picking up
minerals, particularly calcium and magnesium ions, through
dissolution.
2. Calcium carbonate (CaCO₃) and magnesium carbonate
(MgCO₃) are common minerals that contribute to water
hardness.
2.Calcium and Magnesium Ions:
1. Calcium (Ca²⁺) and magnesium (Mg²⁺) ions are positively
charged ions that are soluble in water.
2. These ions are derived from the breakdown of minerals in
geological formations.
3.Ion Exchange:
1. Water hardness is often expressed in terms of calcium
carbonate equivalent (CaCO₃eq), which represents the
concentration of calcium and magnesium ions.
2. When hard water is treated, ion exchange processes are
commonly employed to remove calcium and magnesium
ions and replace them with other ions, often sodium ions.
8. Experiment
Here's a simple experiment that we can conduct to analyze
the hardness of water:
Materials:
1.Water samples (hard water and soft water for comparison)
2.Soap
3.Distilled water (for control)
4.Erlenmeyer flasks or beakers
5.Titration equipment (burette, pipette)
6.Eriochrome Black T indicator solution (or other suitable water
hardness indicator)
7.EDTA (Ethylenediaminetetraacetic acid) solution as the titrant
8.pH buffer solution (optional)
9. Procedure
Preparation:
1.Label the Erlenmeyer flasks or beakers for each water
sample: one for hard water, one for soft water, and one for the
control (distilled water).
2.If using tap water, filter it to remove any suspended particles.
Soap Test:
1. Fill three small containers with equal volumes of each
water sample: hard water, soft water, and distilled water
(control).
2. Add a small amount of soap to each container and observe
the lathering.
3. Hard water will show reduced lathering, and a scum or
precipitate may form.
4. Soft water (or distilled water) should produce more lather
without a scum.
10. Experiment
Titration for Calcium and Magnesium Ions:
Take samples of hard water and soft water for titration. The
titration will determine the concentration of calcium and
magnesium ions.
Add a few drops of Eriochrome Black T indicator to the water
samples. The indicator will change color when all calcium and
magnesium ions are complexed with EDTA.
Titrate each water sample with the EDTA solution until the
color changes. Record the volume of EDTA solution used.
Repeat the titration for accuracy.
11. Calculation
Calculate the concentration of calcium and magnesium ions
in each water sample based on the volume of EDTA used and
the known concentration of the EDTA solution.
Notes:
• Hard water will require more EDTA solution for titration
compared to soft water.
• The soap test provides a qualitative assessment of water
hardness, while titration offers a quantitative measure.
13. Bibliography
Hard water is water that contains large amounts of calcium
(Ca), magnesium (Mg), or iron (Fe) ions; as opposed to soft
water that does not contain large amounts of such minerals.
Hard water is undesirable since it often has an unpleasant
taste, interferes with the ability of soaps to dissolve (although
some synthetic detergents dissolve well in hard water), and
can cause scaling (the building up of insoluble precipitates) in
pipes and hot water systems. On the other hand, hard water
is generally not dangerous to human safety or health.
