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Solubility of Group 2 Hydroxides

The solubility of Group 2 hydroxides increases down the group.Magnesium hydroxide has very low solubility in water.Calcium hydroxide is only slightly soluble in water. The product is called limewater and is used as a test for carbon dioxide.The solubility of group 2 hydroxides increases down the group.
Magnesium hydroxide is only slightly soluble in water with a pH of about 10. Barium hydroxide is much more soluble with a pH of about 13.

Milk of Magnesium

Milk of Magnesia is a saturated solution of magnesium hydroxide mixed with solid magnesium hydroxide. It acts as an antacid neutralising the HCl in the stomach to relieve the symptoms of indigestion. The low solubility of magnesium hydroxide means there is a low concentration of OH- ions which poses no risk to health.Mg(OH)2 (s) + 2HCl (aq) → MgCl2 (aq) + 2H2O (l)

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Specification: OCR Chemistry A (H032), AS-level, 3.1.2 Group 2. Topic: Reactivity Trends.

Key terms in this lesson

Ion
A positively or negatively charged atom or group of atoms, formed by the loss or gain of electrons.
Group
A vertical column of the periodic table, containing elements with the same number of outer-shell electrons.

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