Consider the following statements :
1. The temporary hardness in water is due to the presence of bicarbonates of calcium.
2. The permanent hardness in water is due to the presence of soluble chlorides and sulphates of calcium and magnesium.
3. The permanent hardness in water is removed by adding \(Na_2CO_3\) to water.
Which of the statements given above are correct ?
Water Hardness Statements Analysis
Let's evaluate each statement regarding water hardness:
Statement 1: Temporary Hardness Cause
Temporary hardness is indeed caused by the presence of dissolved bicarbonates of calcium (\(Ca(HCO_3)_2\)) and magnesium (\(Mg(HCO_3)_2\)). This type of hardness can often be removed by boiling.
Statement 1 is correct.
Statement 2: Permanent Hardness Cause
Permanent hardness results from the presence of soluble chlorides (\(Cl^-\)) and sulphates (\(SO_4^{2-}\)) of calcium (\(Ca^{2+}\)) and magnesium (\(Mg^{2+}\)) in water. These salts do not precipitate upon boiling.
Statement 2 is correct.
Statement 3: Removing Permanent Hardness
Permanent hardness is characterized by the presence of \(Ca^{2+}\) and \(Mg^{2+}\) ions. Adding sodium carbonate (\(Na_2CO_3\)) introduces carbonate ions (\(CO_3^{2-}\)), which react with these metal ions to form insoluble precipitates:
- \(Ca^{2+}(aq) + CO_3^{2-}(aq) \rightarrow CaCO_3(s)\)
- \(Mg^{2+}(aq) + CO_3^{2-}(aq) \rightarrow MgCO_3(s)\)
The removal of these ions effectively reduces permanent hardness. This method is part of the lime-soda process.
Statement 3 is correct.
Conclusion
Since all three statements (1, 2, and 3) are correct descriptions of water hardness causes and treatment, the correct option includes all of them.
Similar Questions
‘German silver’ is used to make decorative articles, coinage metal, ornaments, etc. The name is given because:
Which among the following methods is used to separate the constituents present in compound?
Which one of the following statements regarding acids is not correct?
School bells are made of metals because metals are
Which one of the following is used in soda-acid fire extinguishers?
Bright light is found to emit from photographer’s flashgun. This brightness is due to the presence of which one of the following noble gases?
Which of the following substances cause temporary hardness in water?
1. Mg(HCO 3) 2
2. Ca(HCO 3) 2
3. CaCl 2
4. MgSO 4
Select the correct answer using the code given below.
Important Questions from Chemistry in Everyday Life
The plastics which get deformed easily on heating are known as:
CNG stands for which among the following?
Milk becomes sour if kept outside the refrigerator in summer because of:
Which of the following is a ferrous mineral?
Which among the following methods do most Indian households use for obtaining safe drinking water?
