Water Hardness Causes Explained
Water hardness is defined by the concentration of dissolved minerals in it. Primarily, it relates to the amount of multivalent cations dissolved in water.
Identifying Hardness-Causing Ions
- The main cause of water hardness is the presence of dissolved Calcium ions (Ca2+) and Magnesium ions (Mg2+).
- When water flows through rocks like limestone or dolomite, it dissolves these minerals, increasing the concentration of calcium and magnesium.
- These specific ions react with soap to form scum and reduce lathering, which is the common indicator of hard water.
Evaluating Other Ion Options
- While Strontium (Sr2+) is chemically similar to Calcium and can contribute slightly, it's far less common.
- Sodium (Na+) and Potassium (K+) ions are monovalent and generally don't contribute to hardness.
- Chloride (Cl-) and Nitrate (NO3-) / Nitrite (NO2-) ions are anions and do not cause hardness.
Therefore, the hardness of water is primarily due to Calcium and Magnesium ions.
Important Questions from Water Treatment
In the flocculation method of water treatment ______ chemical is added to water.
Which of the following is NOT a chemical coagulant used in water treatment?
Which laboratory test is done to determine approximately the dosage of coagulant?
Statement I): Softening of clear groundwater should be carried out immediately after collection by pumping out, or from springs.
Statement II): Iron and manganese precipitates can foul the exchange medium surface if oxidation occurs in, or prior to, the ion-exchange phase.
Which process is used in water purification?
A. Osmosis
B. Reverse Osmosis
C. Cytolysis
D. Turgor pressure
