Multiple Choice
Which of the following is NOT a sign of having hard water?
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1. Intro to General Chemistry
Chemical Properties
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Hard water mostly contains which of the following minerals?
A
Calcium and magnesium salts
B
Iron(III) oxide
C
Potassium nitrate
D
Sodium chloride
Verified step by step guidance1
Understand that hard water is water that contains high concentrations of certain dissolved minerals, which affect its properties such as soap lathering and scaling in pipes.
Recall that the primary minerals responsible for water hardness are typically metal ions that form salts, especially those that come from the dissolution of minerals in rocks.
Identify that calcium (Ca^{2+}) and magnesium (Mg^{2+}) ions are the most common contributors to water hardness because they form insoluble salts that cause the characteristic effects of hard water.
Recognize that other options like Iron(III) oxide (Fe_2O_3), Potassium nitrate (KNO_3), and Sodium chloride (NaCl) are not the main contributors to hardness; iron oxides are solids, potassium nitrate is a soluble salt but not related to hardness, and sodium chloride does not cause hardness.
Conclude that hard water mostly contains calcium and magnesium salts, which are responsible for its hardness.
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