Modified Arrhenius Theory, Exercises of Chemistry

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Modified Arrhenius Theory

Arrhenius Theory

 (^) An acid ionizes in water to produce H+ (aq) and an anion:  (^) HCl (aq) ---> H

(aq) + Cl¯(aq)  (^) A base dissociates in water to produce OH¯(aq) and a cation.  (^) NaOH(s) ---> Na+(aq) + OH¯(aq)

Modified Arrhenius (acid)

 (^) An acid ionizes in water by reacting with the H 2 O(l) to produce H 3 O+(aq) and anion: HCl(aq) + H 2 O(l) ---> H 3 O+(aq) + Cl¯(aq) Move H+^ to make H 3 O+

Modified Arrhenius (acid)

 (^) NaHSO 4 (aq) is an acid  (^) Dissociate ionic substance and react an ion (almost always the anion) with water. HSO 4 ¯(aq) + H 2 O(l) ---> H 3 O+(aq) + SO 4 2-(aq) Move H+^ to make H 3 O+

Modified Arrhenius (base)

 (^) Bases that contain hydroxide do not need the modified Arrhenius theory:  (^) Ba(OH) (^) 2(aq) ---> Ba2+(aq) + 2OH¯(aq)

Modified Arrhenius (base)

 (^) Na 2 CO 3 (aq) is a base.  (^) A base reacts with water to produce hydroxide and an ion: CO 3 2-(aq) + H 2 O(l) ---> HCO 3 - (aq) + OH¯(aq) Move H+^ to make OH¯

Example

 (^) Classify baking soda as acid or base.  (^) NaHCO 3 (s) --> Na+(aq) + HCO 3 ¯(aq)  (^) The bicarbonate ion is the acid or base species (sodium is a spectator).

Acid

HCO 3 ¯(aq) + H 2 O(l) ---> CO 3 2-(aq) + H 3 O+(aq) Move H+^ to make H 3 O+

Which is it?

 (^) Litmus test in a NaHCO 3 solution:  (^) Blue stays blue  (^) Red turns blue  (^) NaHCO 3 is a base

Neutralization Reaction

 (^) A neautralization reaction is a reaction between an acid and a base: HCl ( aq ) + NaOH ( aq ) → NaCl ( aq ) + HOH ( l ) The products are water and a “salt”. Chemist use “salt” to mean any ionic substance, not just NaCl.

Neutralization

 (^) … can now be defined as the reaction between hydronium and hydroxide ions to produce water.

Your turn

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