Acids Bases and Salts

Chapter Summary

Acid Base Indicators

Dyes or mixtures of dyes which are used to indicate the presence of acids and bases are called acid-base indicators.

Examples: Litmus, Methyl Orange, Phenolphthalein

Acidic and Basic Nature

An acidic substance forms H+ ions in aqueous solution, to show acidic nature.

A basic substance forms OH- ions in aqueous solution, to show basic nature.

Acids and bases conduct electricity in aqueous solution because they form ions in aqueous solution.

Reaction with Metals

When an acid reacts with a metal, hydrogen gas is evolved and a salt of the metal is formed.

Acid + Metal → Salt + Hydrogen

When a base reacts with a metal, hydrogen gas is evolved and a salt is formed. This salt is has a negative ion composed of metal and oxygen.

Reaction with Carbonates

When an acid reacts with a metal carbonate or metal hydrogen carbonate (bicarbonate), a salt, carbon dioxide and water are formed.

Acid + Metal Carbonate → Salt + CO2 + H2O

pH Scale

pH scale shows strength of acid or alkali, by showing the measure of hydrogen ion concentration in a solution.

The range of pH scale is from 0 to 14

pH of neutral solution is equal to 7, pH of acidic solution is less than 7 and pH of alkaline solution is more than 7

Chemicals from NaCl

Caustic Soda: Made by electrolytic decomposition of brine.

Bleaching Powder: Made by reaction between slaked lime and chlorine gas.

Baking Soda: Made by reaction of brine with carbon dioxide and ammonia. This reaction is called Solvay Process.

Useful Chemicals

Baking Powder: It is a mixture of baking soda and edible acid. Edible acid prevents bitterness in cooked dish.

Washing Soda: Obtained by thermal decomposition of sodium bi-carbonate.

Plaster of Paris: Made by heating gypsum CaSO4.2H2O, used for making plaster cast