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Group 2, the Alkaline Earth Metals
9.1: Physical and Chemical Properties…
Group 2, the Alkaline Earth Metals
9.1: Physical and Chemical Properties of Group 2
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Melting Points: High (giant structures). Going down, electrons in delocal sea are further from positive nuclei so strength of bonds decrease going down so MP decrease going down. Mg doesn't fit the trend
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Reactions with Water
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Magnesium hydroxide (milk of magnesia) used in indigestion to neutralise stomach acids causing heartburn, indigestion and wind. Mg reacts very slowly with cold water but rapidly with steam to form an alkaline oxide and H
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Solubilities of Sulfates
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Barium sulfate is virtually insoluble so it can be taken by mouth to outline the gut in x-rays. It is safe despite the fact that barium compounds are highly toxic as barium sulfate is so insoluble
Insolubility of barium sulfate also used in test for sulfate ions in a solution. Solution is first acidified with nitric or hydrochloric acid and barium chloride is added. If sulfate ions are present as white precipitate of barium sulfate is formed
Addition of acid removes carbonate ions as carbon dioxide (BaCO3 is also white and insoluble which is indistinguishable from BaSO4)