Non-metals react with H2O and acids

Reactions of acids and metals

Redox reactions between hydrogen ions and metal atoms

Magnesium, iron and zinc are dissolved by hydrochloric acid and dilute sulfuric acid and hydrogen is released. Copper does not show this behavior. Metals that are broken down by acids to release hydrogen are known as base metals. The evolution of hydrogen during the reaction of base metals with dilute acids has long been considered a typical acid characteristic.

The chemical process that takes place in this reaction is obvious: if one assumes that hydrated protons are present in an aqueous acid solution, hydrogen atoms are formed from protons by accepting electrons. The absorbed electrons were given off by the atoms of the base metals, which then became ions.


$ \ mathrm {\ underbrace {2 \ H ^ {+} _ {(aq)}} _ {\ mathsf {hydrogen ion}} + \ underbrace {Mg} _ {\ mathsf {magnesium atom}} \ \ xrightarrow \ \ underbrace { H_ {2}} _ {\ mathsf {hydrogen molecule}} \ \ + \ \ \ underbrace {Mg ^ ​​{2 +} _ {(aq)}} _ {\ mathsf {magnesium ion}}} $


The entire chemical process is therefore a redox reaction:


Reduction: $ \ \ \ qquad \ mathrm {2 \ H ^ {+} + e ^ {-} \; \ longrightarrow \; H: H} $

Oxidation: $ \ \ \ qquad \ mathrm {\ Mg: \ quad \ quad \; \; \; \ longrightarrow \; Mg ^ {2+} + 2 \ e ^ {-}} $

Redox reaction: $ \ mathrm {\ underbrace {Mg} _ {\ mathsf {Magnesium}} \ + \ \ underbrace {2 \ H ^ {+}} _ {\ mathsf {Hydrogen ion}} \; \ longrightarrow \; \ underbrace {Mg ^ ​​{2 +}} _ {\ mathsf {Magnesiumion}} + \ underbrace {H_ {2}} _ {\ mathsf {Hydrogen}} \ \ uparrow} $


The atoms of the noble metals, such as copper, do not enter into any redox reactions with hydrogen ions, as experiment 1 has shown.



Salt formation when acids react with metals

In an aqueous acid solution, in addition to the hydrated protons, there are always also the hydrated anions that are formed after the hydrogen ions have been split off from the acid molecule (Chapter 42) (acid residues). These anions of the acids are not involved in the redox process between the protons and the metal atoms. If the solutions that arise when metals dissolve in dilute acids are evaporated, salts crystallize out. I. E. the resulting metal ions form the ion lattice of a salt with the acid residues. The magnesium ions produced in experiment 1 form the salt magnesium chloride with the chloride ions.


To solve:

$ \ mathrm {\ underbrace {Mg} _ {\ mathsf {Magnesium}} + \ underbrace {2 \ H ^ {+} _ {(aq)} + 2 \ Cl ^ {-} _ {(aq)}} _ {\ mathsf {Hydrochloric acid}} \ \ xrightarrow \ \ underbrace {Mg ^ ​​{2 +} _ {(aq)} + 2 \ Cl ^ {-} _ {(aq)}} _ {\ underset {\ large \ mathsf {chloride}} {\ mathsf {Magnesium-}}} + \ underbrace {H_ {2} \ \ uparrow} _ {\ underset {\ large \ mathsf {atom}} {\ mathsf {Hydrogen-}}}} $


Crystallize (evaporation):

$ \ mathrm {\ underbrace {Mg ^ ​​{2 +} _ {(aq)} + 2 \ Cl ^ {-} _ {(aq)}} _ {dissolved \ magnesium chloride} \ qquad \ xrightarrow {-H_ {2} O} \ qquad \ underbrace {MgCl_ {2}} _ {solid \ magnesium chloride}} $


The name of the salt is obtained by adding the acid residue name to the metal name.




To solve:

$ \ mathrm {\ underbrace {Zn} _ {zinc} + \ underbrace {2 \ H ^ {+} _ {(aq)} + 2 \ NO ^ {-} _ {3 \ (aq)}} _ {nitric acid } \; \ longrightarrow \; \ underbrace {Zn ^ {2 +} _ {(aq)} + 2 \ NO ^ {-} _ {3 \ (aq)}} _ {dissolved \ zinc nitrate} + \ underbrace {H_ {2} \ \ uparrow} _ {Hydrogen}} $


Crystallize (evaporation):

$ \ mathrm {Zn ^ {2 +} _ {(aq)} + 2 \ NO ^ {-} _ {3 \ (aq)} \ qquad \ xrightarrow {-H_ {2} O} \ qquad \ underbrace {Zn (NO_ {3}) _ {2}} _ {zinc nitrate}} $


To put it simply, one writes:

$ \ mathrm {\ underbrace {Zn} _ {zinc} + \ underbrace {2 \ HNO_ {3}} _ {nitric acid} \ qquad \ longrightarrow \ qquad \ underbrace {Zn (NO_ {3}) _ {2}} _ {Zinc nitrate} + \ underbrace {H_ {2} \ uparrow} _ {hydrogen}} $


Another example:

This notation does not specifically express protolysis and hydration in water.

$ \ mathrm {\ underbrace {Zn} _ {zinc} + \ underbrace {2 \ HCl} _ {hydrochloric acid} \ qquad \ longrightarrow \ qquad \ underbrace {ZnCl_ {2}} _ {zinc chloride} + \ underbrace {H_ {2 } \ uparrow} _ {hydrogen}} $