Question
Hardness of water is due to the presence of
The correct answer is
Calcium and Magnesium ions
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.
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Important Questions from Water Treatment
- Choose the correct statements about coagulation process.
A. Coagulation makes smaller colloids to adhere to each other to form large floc particles
B. Colloids are continually involved in Brownian moment.
C. Colloids are stable because of their surface charge.
D. Coagulants are preferably trivalent cations.
E. Coagulants are soluble in neutral pH.
Choose the most appropriate answer from the options given below: - Which of the following is used as a coagulant for removal of phosphates in water ?
- Given the following parameters of a primary settling chamber :
Diameter = 50m, Depth = 2.5m, average detention time = 2 hours.
How much quantity of waste water is being treated ? - Calculate hardness in units of mg/l as CaCO$_3$ of a ground water sample having Ca$^{++}$ ion concentration of 100 mg/l.
- Choose the correct statements
A. Temperature has a effect in disinfection treatment of water.
B. pH controls the amount of HOCl and OCl in water.
C. Cl$_2$ gas used for disinfection forms HCl as a product in water.
D. Disinfection action is because of HOCl formed and not due to Cl$_2$ gas.
E. Combined chlorine exist in water due to combination of HOCl with NH$_3$ and organic compounds.
Choose the correct answer from the options given below:
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