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Question
Which of the following ions will cause hardness in water sample?
Options
\[\ce{Ca^{2+}}\]
\[\ce{Na+}\]
\[\ce{Cl-}\]
\[\ce{K+}\]
Solution
\[\ce{Ca^{2+}}\]
Explanation:
\[\ce{Ca++}\] ions in the form of \[\ce{Ca(HCO3)2}\] or \[\ce{CaCl2}\] or \[\ce{CaSO4}\] cause hardness in water, i.e., soluble salts of calcium can cause hardness in water.
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