Why can't Mg(OH)2 act as a buffer?

Asked by travelbabe24 (262

) April 5th, 2016 from iPhone

I’m so confused. Buffers consist of a weak acid/base and forms it’s conjugate base/acid in solution. Mg(OH)2 is a weak base, and when a strong acid is added to it, it forms it’s conjugate weak acid and water. Since it’s a conjugate acid and base, wouldn’t that make it a buffer?

I’ve been on this homework question forever and just need an explanation. Mg(OH)2 is an antacid by the way.

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6 Answers

http://www.jiskha.com/display.cgi?id=1427999118

Rarebear (25192

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Buffers are matched to the pH of the solution being examined. Not always weak. A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it.

http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Acids_and_Bases/Buffers

http://www.chemguide.co.uk/physical/acidbaseeqia/buffers.html

I think the second link will help you figure out your problem. It lies with the two terms of ‘equilibrium’ and ‘equilibria’. A good buffer removes some of the hydrogen ions, but not all. MgOH2 exhausts itself completely and finds ‘equilibrium’. Magnesium is not very soluble.

cazzie (24516

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Sorry, I hit send before I finished. Magnesium is a metal, not a salt.

cazzie (24516

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@cazzie all salts are made from ionized metals

Rarebear (25192

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Yes, meaning that Magnesium, Mg alone, is a metal. MgSO4 is a salt.