Group P:copper,magnesium,zinc Name a suitable reagent that can be added to help him select the one substance which is chemically different from the other two.  Please state the expected...

Group P:copper,magnesium,zinc

Name a suitable reagent that can be added to help him select the one substance which is chemically different from the other two.  Please state the expected observations for the three substances in group P, using the previous reagent ,and thus deduce which solid is different from the others.  Explain the difference in reaction observed.

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ncchemist | eNotes Employee

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We have copper, magnesium, and zinc as solid metals.  There is a reagent that will react with two of these but not the third one.  That reagent is HCl, or hydrochloric acid.  HCl will react with zinc and magnesium, but not with copper.  The reactions for magnesium and zinc are below:

Zn + 2HCl --> ZnCl2 + H2

Mg + 2HCl --> MgCl2 + H2

Both metals will dissolve in aqueous HCl to give the corresponding chloride salts and hydrogen gas.  Both of these metals are oxidized by the acid.  But copper is less reactive and not as easily oxidized.  So copper will give no reaction in HCl.  The actual observations are that zinc and magnesium will dissolve in the acid and disappear while at the same time the hydrogen gas bubbles out from the liquid.  But the copper will simply sit in the acid and not dissolve or bubble.

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