This PSEB 10th Class Science Notes Chapter 2 Acids, Bases and Salts will help you in revision during exams.
PSEB 10th Class Science Notes Chapter 2 Acids, Bases and Salts
→ The sour taste of foods is due to acids and the bitter taste is due to bases present in them. Acids turn blue litmus into red and bases turn the red litmus into the blue.
→ Acids and bases neutralize each other’s effects.
→ Acids and bases can be tested using litmus, turmeric, methyl orange, and phenolphthalein indicators.
→ On passing carbon dioxide gas through lime water, lime water turns milky.
→ On passing, excess carbon dioxide gas through lime water, its milky colour disappears due to the formation of soluble calcium bicarbonate.
→ Bases turn phenolphthalein pink in colour.
→ Acids and bases react to produce salt and water.
→ The flow of current in the solution is due to ions present in the solution.
→ In acids H+ ions are present. Acids produce hydrogen ion H+(aq) in a solution due to which solutions become acidic.
→ Bases produce hydroxide (OH–) ions in water.
→ Alkali is a base that dissolves in water.
→ Bases are soapy to touch, bitter, and corrosive.
→ All acids produce H+(aq) and bases produce OH–(aq) in an aqueous solution.
→ The process of the dissolving of acids or bases in water is highly exothermic, therefore to dilute them these should be added and mixed slowly in water. Never add water to concentrated acid.
→ A universal indicator is a mixture of several indicators.
→ Universal indicators show different colors for different concentrations of hydrogen ions in the solution.
→ A scale known as the pH scale has been developed for measuring the concentration of hydrogen ions present in the solution.
→ The ‘p’ in pH stands for ‘potenz’ this is a German word which means power.
→ On the pH scale, we can measure pH generally from 0 (very acidic) to 14 (very basic).
→ Higher is the concentration of hydronium ion, less is the value of pH. A neutral solution has a pH value of 7.
→ If the value of pH is less than 7 then the solution is acidic and if pH lies between 7 to 14 then the solution is basic.
→ Those acids which produce a large number of H+ ions are called strong acids and those acids which produce less H+ ions are weak acids.
→ Our body works in the range of 7.0 to 7.8.
→ When the pH value of rainwater is less than 5.6 it is called acid rain.
→ To get rid of acidity in the body, and antiacid like magnesium hydroxide which is a weak base is used.
→ If the pH value is less than 5.5 in the mouth, decay of teeth starts.
→ Nettle is a herbaceous plant that causes painful stings due to methanoic acid present in stinging hair. A traditional remedy is rubbing the area with the leaf of the dock plant.
→ Common salt (NaCl) is produced by the reaction between hydrochloric acid and sodium hydroxide.
→ Bleaching powder is produced by the action of chlorine on dry slaked lime.
→ Bleaching powder is used in the paper and textile industry for bleaching. It acts as an oxidant and as a disinfectant.
→ Baking soda (NaHCO3) is produced from sodium chloride.
→ Sodium hydrogen carbonate is a mild non-corrosive base. It is used in the production of Baking powder and used in the preparation of cakes. It is also used in fire extinguishers.
→ Washing soda (NagCO3.10H2O) is prepared from sodium chloride. It is used in the glass, soap, paper industries. It is used to remove the permanent hardness of the water.
→ The chemical formula for hydrated copper sulfate is CuSO4.5H2O and of gypsum is CaSO4.2H2O.
→ Plaster of Paris is obtained from calcium sulphate hemihydrate (CaSO4. \(\frac{1}{2}\) H2O) by heating it at 373K.
→ Plaster of Paris is used for making toys and material for decoration.
→ Indicators: These are the substances that give different colors in acidic and basic solutions e.g. litmus, turmeric, phenolphthalein, methyl orange, etc.
→ Olfactory Indicators: There are some substances whose odour changes in acidic or basic media, which are known as olfactory indicators.
→ Acid: Those compounds which have one or more hydrogen atoms and which give hydrogen (H+) or hydronium (H3O+) ions (H3O+) ion in an aqueous solution are called acids. These are sour in taste.
→ Ionization: It is a process in which a substance produces ions in water, ionization.
→ Basicity of an acid: Basicity of an acid is the number of hydronium ions [H+] produced when one molecule of acid gets completely ionized in an aqueous solution.
→ Base: Bases are those compounds which are metal oxides or metal hydroxide or aqueous ammonia and these react with hydronium ion (H3O+) of acids to produce salt and water.
→ Neutralization: Due to the reaction between acids and bases, salt and water are produced. This is called a neutralization reaction.
→ Alkali: Those basic hydroxides which on dissolving in water form hydroxyl (OH–) ions, are called alkali.
→ Universal indicator: It is a mixture of various organic substances which show different colours with solutions having different pH values.
→ Dissociation: When a molecule or ionic compound dissociates into two or more atoms or ions, this is called dissociation.
→ Chemical dissociation: A reaction in which a molecule of a compound breaks into atoms or ions is called chemical dissociation.
→ The water of Crystallisation: Water, which is present in crystals of a substance is called water of crystallization. e.g., FeSO4.7H2O, Al2O3.2H2O, CuSO4.5H2O, Na2CO3.10H2O.
→ Efflorescence: The process of release of crystalline water from hydrated salts into the air is called efflorescence.
→ Deliquescence: This is a process in which a substance absorbs moisture from the atmosphere and dissolves in the absorbed water to form a solution.
→ Dilution: On mixing acid or base in water, the concentration of ions (H3O+/OH–) per unit volume becomes less. This is called dilution.
→ Chlor-alkali process: The electrolysis of sodium chloride solution is called chlor-alkali process.