Chapter 7: Acids, bases and salts
Strong acid
An acid that completely disassociates in aqueous solution to form H+ ions.
Weak Acid
An acid that partially disassociates in aqueous solution to form H+ ions.
Alkalis
Aqueous solutions of bases contain OH- ions.
Effect of litmus on Acid and Base
Acid - Red
Base - Blue
Neutral - Purple
Effect of Thymolphthalein on Acid and Base
Acid - Colourless
Base - Blue
Effect of Methyl Orange on Acid and Base
Acid: Red
Base : Yellow
Acids and Metals
1) Only metals above hydrogen in the reactivity series will react with dilute acids. (MAZIT metals)
Acid + Metal → Salt + Hydrogen
2) Soluble salt is prepared by filtration -> evaporation -> crystallisation
Acid and Bases
1) Metal oxides and metal hydroxides (alkalis) can act as bases
2) When they react with acid, a neutralisation reaction occurs
Acid + Base → Salt + Water
3) The soluble salt can be prepared by evaporation -> crystallisation
Acid and carbonate
Acid + Metal Carbonate → Salt + Carbon Dioxide + Water
1) Soluble salt can be prepared by Filtration -> Evaporation -> Crystallisation.
Base and ammonium salt.
1) Ammonium salts undergo decomposition to form ammonia when warmed with an alkali
Ammonium Salt+ Alkali → Salt+ Water+ Ammonia
2) Presence of ammonia can be checked by turning damp red litmus blue.
Non-metallic oxides are....
Acidic, including SO2 and CO2.
Metallic oxides are....
Basic, including CuO and CaO
Amphoteric oxides are...
Oxides that react with BOTH acids and bases to form salt + water.
Eg. Al2O3 and ZnO (Aluminium oxide, zinc oxide)
Preparation of insoluble salt
1) Made by precipitation
Soluble salt (AX) + Soluble Salt (BY) -> Soluble Salt (AY) + Insoluble Salt (BX)
2) Insoluble salt can be prepared by Filtration -> Washing -> Drying
Hydrated, Anhydrous, Water of crystallisation
Hydrated - Chemically combined with water
Anhydrous - Substance containing no water
Water of crystallisation - Water molecules present in hydrated crystals.
Solubility Rules for salts
1) Sodium, Potassium, Ammonium Salts are soluble
2) Nitrates are soluble
3) Chlorides are soluble except lead and silver
4) Sulfates are soluble except barium, calcium and lead
5) Carbonates are insoluble except sodium, potassium and ammonium
6) Hydroxides are insoluble, except sodium, potassium, ammonium and calcium