Page 34 - Curriculum Visions Dynamic Book

Magnesium
Magnesium, like calcium, is a highly reactive element, readily combining with other elements to make compounds.
Magnesium is a silvery metal, not unlike calcium but easier to extract from its ore. It is the most reactive of the metals that can be used in everyday applications (calcium, sodium and potassium are too difficult to produce and are unstable in air, water or both).
The reactivity of magnesium can easily
be demonstrated by lighting a taper made of magnesium ribbon. It rapidly bursts into flame giving out a bright white light. (This used to be used for flashlight bulbs; it is still used in signal flares.) Similarly, magnesium reacts quickly with dilute hydrochloric acid, giving off hydrogen gas.
 Magnesium ribbon. Magnesium reacts with the oxygen of the air and develops a dull oxide coating. The end of this sample has been cleaned with emery paper to show the nature of untarnished metal. The white fragments are of magnesium oxide, formed as the result of burning part of the ribbon
(as shown right). The rapid oxidation of the ribbon as it burns is shown by the small pieces of ribbon that are still bright and shiny where the tongs were holding it in the flame.
 When magnesium ribbon is dropped into dilute hydrochloric acid, a reaction takes place in which hydrogen gas is given off along with
a lot of heat.
 The most widespread natural use of magnesium is in the chlorophyll in leaves. An ion of magnesium lies at the center of each chlorophyll molecule.
EQUATION: The reaction of magnesium with an acid
Magnesium + dilute hydrochloric acid ➪ magnesium chloride + hydrogen gas
Mg(s) + 2HCl(aq) ➪ MgCl2(aq) + H2(g)
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