Which of the following statements is false about hard water?

Analysis of the Question

The question asks us to identify the false statement regarding hard water among the given options. Hard water is water that contains high concentrations of dissolved minerals, specifically calcium ($Ca^{2+}$) and magnesium ($Mg^{2+}$) ions.

Concept Explanation

To solve this, let's evaluate the properties of hard water:

• Biological Benefits: Hard water contains calcium and magnesium ions. Calcium is essential for the development and maintenance of strong bones and teeth in animals and humans. Therefore, consuming hard water is generally considered beneficial for skeletal health.
• Taste: Many people prefer the taste of hard water over soft water because the dissolved minerals give it a distinct, "refreshing" mineral taste compared to the "flat" taste of soft water.
• Interaction with Pipes: Hard water is generally less corrosive than soft water. Soft water (which is often acidic) tends to dissolve lead from lead pipes, leading to lead poisoning. Hard water, however, often forms a protective layer of calcium carbonate ($CaCO_3$) inside pipes, which prevents the leaching of lead. Therefore, hard water is actually safer to transport through lead pipes than soft water.

Step-by-Step Evaluation

• Option A: True. The calcium content helps in the formation of strong teeth.
• Option B: False. Hard water is not prohibited from being supplied in lead pipes; in fact, it is safer than soft water because the mineral deposits form a protective coating that prevents lead from dissolving into the water.
• Option C: True. The mineral content is widely considered to improve the taste of drinking water.
• Option D: True. Similar to teeth, the calcium in hard water is vital for bone density and strength.

Conclusion

Since options A, C, and D are scientifically accurate descriptions of the benefits and properties of hard water, option B is the incorrect statement.

Exam Tip

When dealing with "Which of the following is false/not true" questions, always look for the statement that contradicts established scientific facts. Remember the mnemonic "Hard water = Healthy bones/teeth, but bad for soap"—this helps you quickly identify benefits versus industrial disadvantages (like scale formation in boilers).