These comprehensive RBSE Class 10 Science Notes Chapter 2 Acids, Bases and Salts will give a brief overview of all the concepts.
RBSE Class 10 Science Chapter 2 Notes Acids, Bases and Salts
→ Acids are sour in taste and turns blue litmus paper into red.
→ Bases are bitter in taste and turns red litmus paper into blue.
→ Acid base indicators are dyes or mixtures of dyes which are used to indicate the presence of acids and bases.
→ The substances whose odour changes in acidic or basic media are called olfactory indicators.
→ Litmus solution is a purple dye, which is extracted from lichen, a plant belonging to the division Thallophyta, and is commonly used as an indicator.
→ Acids forms H+(aq) ions in aqueous solution and bases forms OH–(aq) ions in aqueous solution.
→ When an acid reacts with a metal, hydrogen gas is evolved and a corresponding salt is formed
→ When a base reacts with a metal, along with the evolution of hydrogen gas a salt is formed but such reactions are not possible with all metals
→ When an acid reacts with a metal carbonate or metal hydrogencarbonate, it gives the corresponding salt, carbon dioxide gas and water.
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
→ Neutralisation reaction-Acids and Bases reacts with each other to form salt and water, this reaction is called neutralisation reaction. This is exothermic reaction.
→ NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
→ Metal oxides are generally basic so they reacts with acids and form salt and water.
→ Non-metal oxides are acidic so they reacts with bases and form salt and water.
→ Aqueous solution of acids, bases and salts conduct electricity because free ions are present in these solutions due to which current is passed.
→ Alkali-Bases which are soluble in water are called Alkali. These are corrosive in nature.
→ When water is added in Acidic or Basic solution, (H2O+/OH–) ion concentration per unit volume is decreased. This process is called dilution.
→ The process of dissolving an acid or a base in water is a highly exothermic one.
→ The strength of an acid or an base can be tested by using a scale called the pH scale (0-14) which gives the measure of hydrogen ion concentration in a solution.
→ A neutral solution has a pH of exactly 7, while an acidic solution has a pH less than 7 and a basic solution has a pH more than 7.
→ Acids are of two types-strong acid and weak acid. The acids which gives more number of H+ ion in solution are called strong acids and the acids which gives less number of H+ ion in solution are called weak acids.
→ Similar to acids, bases are also of two types-strong base and weak base which gives more and less number of OH ions in solution respectively.
→ Living beings carry out their metabolic activities within an optimal pH range.
→ Acid rain-When the pH of rain water becomes less than 5.6 then this is called acid rain. The survival of aquatic life in such water becomes difficult.
→ Tooth decay starts when the pH of the mouth is lower than 5.5.
The pH of solutions of different salts are different which depends on acid and base by which that salt is formed. For example pH of the solution of salt formed with strong acid and strong base is 7.
→ The common salt is an important raw material for various materials of daily use, such as sodium hydroxide, baking soda, washing soda, bleaching powder and many more.
→ Chlor-alkali Process – When electricity is passed through an aqueous solution of sodium chloride, it decomposed to form NaOH, this process is called chlor-alkali process. Cl2 and H2 are also formed in this process.
→ Bleaching Powder (CaOCl2) is used for bleaching clothes etc. and for disinfecting
drinking water.
Bleaching Powder is prepared by the reaction of dry slaked lime with chlorine.
Ca(OH)2 + Cl2 → CaoCl2 + H2O
→ The formula of washing soda is Na2CO3 · 10 H2O, baking soda is NaHCO3 and Plaster of Paris is CaSO4 . \(\frac{1}{2}\)H2O.
→ Salts are very useful in everyday life and industries. Large crystals of NaCl are brown due to impurities, this is called rock salt.
→ Water of crystallisation-The fixed number of water molecules present in one formula unit of a salt in its crystalline form is called water of crystallisation.
→ The formula of Gypsum is CaSO4 . 2H2O. On heating gypsum it loses water molecules and becomes calcium sulphate hemihydrate (CaSO4. \(\frac{1}{2}\)H2O) . This is called Plaster of Paris.
→ Plaster of Paris is used for making toys, materials for decoration, etc.
Leave a Reply