Question.1: Explain Arrhenius concept of acid & base.

Ans.: According to Arrhenius concept, the acids and bases are defined as follows:

Acid: An acid is regarded as a hydrogen containing substance, which gives off hydrogen ion (H+) dissociating in the aqueous solutions. Actually an acid produces H30+ (hydronium ion) in water. Arrhenius concept is based upon ionic dissociation of compound in water.

Thus HCl is an acid because it produces H+ ion in water:

HCl  +   H2O →  H+(aq)  +   Cl(aq)

Example: HCI, HNO3, H2SO4, CH3-COOH etc.

In general, HA  +  H2O  →  H+(aq)   +   A(aq)

acid Base: A base is regarded as a hydroxyl group-containing compound, which gives off hydroxyl ions (OH) when dissociated in the aqueous solution. NaOH is a base because it yields OH ion in water.

NaOH  +  H2O  →  Na+(aq)  +  OH(aq)  

Example: NaOH, Ca(OH)2, NH4OH etc.

In general,  BOH  +  H2O  →  B+(aq)   +   OH(aq)

Thus according to Arrhenius concept, Acids give H+ ions in water, bases give OH ions in water |

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