acids , bases and salts

• Acids turn blue litmus paper red, while bases turn red litmus paper blue.
• bases which are soluble in water are called alkalis
• acid + base = salt + water
• example of acid + base is NaOH + HCl = NaCl + H2O
• acid + metal = salt + H2 gas
• acid + metal oxide = salt + water as metal oxides are basic in nature
• example of acid + metal : Zn + H2SO4 = ZnSO4 + H2
• both acid and bases are electrolytes which means that they are good conductors of electricity
• metal carbonates react with acids to produce salt, water and carbon dioxide gas.
• neutralisation is the reaction between an acid and base where both reactants are completely consumed to form a neutral solution (water).
• a pH less than 7 indicates an acidic solution while a pH greater than 7 indicates an alkaline solution
• those substances whose odor changes in acidic or basic medium are called olfactory indicators
• the indicator phenolphthalein turns pink when it comes into contact with a strong base but remains colorless in weak acid solutions
• methyl orange turns red in acidic solutions and yellow in basic solutions
• when electricity is passes through an aqueous solution of sodium chloride it decomposes to form sodium hydroxide. this process is called chlor-alkali process
• common salt (NaCl) : 2NaCl + 2H2O = 2NaOH + Cl2 + H2
• sodium bicarbonate on heating decomposes to give sadium carbonate and release of H2 gas
• baking soda is sodium bicarbonate, NaHCO3
• baking soda on heating gives a white precipitate of sodium carbonate which is washing soda
• washing soda is sodium carbonate, Na2CO3 . 10H2O
• Plaster of Paris is CaSO4 . 1/2 H2O
• gypsm on heating at 373K loses water molecules and becomes calcium sulfate hemi-hydrate