Acids and Base reactions

Acids are substances that taste sour. eg. citric acid. Bases are substances that taste bitter. eg. Bi-carb of soda. There are many different types of acids and bases and most are too corrosive to taste. The word corrosive means it will eat away. There must be another way to determine whether a chemical substance is acidic or basic.

Indicators are chemicals that change color in the presence of an acid or a base. Pink litmus paper will change to blue in the presence of a base. Blue litmus paper will change to pink in the presence of an acid.

Acids and bases react with each other to produce water and a salt. This type of reaction is called a neutralization reaction. Acid + Base => Salt + Water

An alkali is a strong soluble base. All of the Group I metals or alkali metals produce alkali solutions on reaction with water. eg. lithium hydroixde, sodium hydroxide and potassium hydroxide.

A common neutralization reaction carried out in high school is the neutralization of hydrochloric acid with sodium hydroxide.

Hydrochloric acid + sodium hydroxide => Sodium chloride + Water

2HCl + NaOH => NaCl + H₂O

Bromothymol blue is an excellent indicator to add as it is yellow in acid, blue in base and green when neutral. The solution can be evaporated in a watch glass which is placed on top of a water bath. Salt crystals appear as the water evaporates.

All neutralization reactions are also exothermic meaning heat is given off. Hydrogen ions produced from the acid react with hydroxide ions produced from the base. Energy is released as new chemical bonds are formed as water is produced.

Hydrogen ion + hydroxide ion => water

H⁺(aq)+ OH^-(aq) => H₂O(l)