Question

which are of the following is not the limitat of Arrhenius concept?
a) H+ ions product by acids do na not exist in free state

b)his concept is limited to water only

c)Hcl is an Arrhenius acid

d)some bases do not produce off ions in H20​

Answer 1

Question:

Arrhenius Theory, Its Limitations and Examples

Answer:

What Is Arrhenius Theory?

• The Arrhenius theory was first introduced by the Swedish scientist Svante Arrhenius in the year 1887.
• To conduct electricity, one must have free moving ions.
• Svante Arrhenius noticed that the solution of acid conducts electricity by dissolving the substance in the solution, which dissociates into ions.
• This concept is well-known these days, but during that time it was controversial.
• This theory is known as “Electrolytic dissociation.”
• Water is a neutral substance, which does not conduct electricity.
• By dissolving some substance in water, it conducts electricity.
• These substances are called electrolytes and the process is known as “Electrolytic dissociation.”

Arrhenius Theory of Acid and Base

• According to Arrhenius theory, acid is a substance that gives H+ ion on dissolving in the aqueous solution.
• It increases the concentration of H+ ions in the solution.
• The base is a substance that ionizes OH– ion by dissolving in the aqueous solution.
• The concentration of OH- ions is high in the solution.

Arrhenius acids

• Arrhenius acid in the aqueous solution increases the concentration of protons or H+ ions.
• For example, hydrochloric acid in the water. HCl undergoes dissociation reaction to produce H+ ion and Cl– ion, as explained below.
• The concentration of the H+ ions is increased by forming hydronium ion.

HCl (aq) → H⁺(aq) ⁺ Cl⁻(aq)

HCl (aq) + H2O(l) → H3O⁺(aq) ⁺ Cl⁻(aq)

Other examples of Arrhenius acids are listed below

NHO3(aq) + H2O(l) → H3O⁺(aq) ⁺ No3⁻

In this reaction, nitric acid dissolves in aqueous water to give hydrogen and nitrate ions.

Arrhenius Acids-examples  

Hydrochloric acid (HCl)

Nitric acid (HNO₃)

Sulphuric acid (H₂SO₄)

Phosphoric acid (H₃PO₄)

Carbonic acid (H₂CO₃)

Acetic acid (CH₃COOH)

Arrhenius Base

• An Arrhenius base is a substrate that increases the concentration of hydroxide ions in the aqueous solution.
• The example for Arrhenius base is highly soluble sodium hydroxide compound in water, which dissociates to give sodium ion and hydroxide ion.
• In aqueous solution, NaOH completely dissolves to give hydroxide ion and sodium ion, to increase the concentration of hydroxide ions.

NaOH(aq) → Na+(aq) ⁺OH⁻(aq)

Arrhenius Base  Examples :

Sodium hydroxide - NaOH

Potassium hydroxide - KOH

Calcium hydroxide - Ca(OH)₂

Magnesium hydroxide - Mg(OH)₂

Limitations of Arrhenius theory:

• An acid is expected to be an acid in any solvent. But that’s not the case nowadays. For example HCL acts as an Arrhenius acid when dissolved in water. However when HCL is dissolved in benzene there is no dissociation. This is against Arrhenius theory; Arrhenius states that dissociation occurs in any aqueous solution. The properties of acid and bases play a critical role.

•  Arrhenius did not explain in his theory the behavior of acids and bases in a     non aqueous solution For example, the dissociation of acetic acid in methanol it could be written as CH₃CO₂H + CH₃OH ⇄ CH₃CO₂⁻ + CH₃OH

• In Arrhenius theory all salts should produce solutions that are neither acidic nor basic. But there are some exceptions against this theory. For example if equal amounts of HCl and ammonia react, the solution is slightly acidic. If equal amounts of acetic acid and sodium hydroxide react, the resulting solution is basic. Arrhenius theory does not include any explanation for this.

• The need for hydroxide as the base led Arrhenius to propose the formula NH₄OH as the formula for ammonia in water. This led to the misunderstanding that NH₄OH is the actual base. But the actual base is NH₃.

• As you read before the bare proton H+, cannot exist for a long time in a water solution. Therefore this reaction: H₂O + H⁺ à H₃O+ Occurs most of the time.