Question

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water that contains high concentrations of calcium, magnesium, or iron is called
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Explanation:

Hard water is defined as water that has a high concentration of divalent cations like calcium ($\text{Ca}^{2+}$), magnesium ($\text{Mg}^{2+}$), or iron ($\text{Fe}^{2+}/\text{Fe}^{3+}$). These cations make the water "hard" in the sense that it doesn't lather easily with soap (due to the reaction of these cations with soap molecules to form insoluble precipitates).

Answer:

hard water