Chapter Summary
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
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.
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.
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 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
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.
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