NCERT Solutions Class 10th Science Chapter – 2 Acids Bases and Salts
| Textbook | NCERT |
| Class | 10th |
| Subject | Science |
| Chapter | 2nd |
| Chapter Name | Acids Bases and Salts |
| Category | Class 10th Science |
| Medium | English |
| Source | Last Doubt |
| NCERT Solutions Class 10th Science Chapter – 2 Acids Bases and Salts Notes Why are acids bases and salts important?, What are 5 examples of bases?, What are 3 examples of bases?, What are the examples of salts?, What are the 6 strong bases?, Is a soap a base?, What is pH value of salt?, Is NaCl a base or acid?, Why is sugar a base?, What are the 7 weak acids?, What are 3 weak bases?, What are the 10 weak bases?, What is the pH of milk?, What is the pH of blood?, What pH is lemon?, What pH is sugar?, What pH is water?, Why is H2SO4 called an acid?, What is the pH of banana?, What is the pH of Coca Cola?, What is the pH of apple?, What is the pH of papaya? and What is the pH of honey? etc. |
NCERT Solutions Class 10th Science Chapter – 2 Acids Bases and Salts
Chapter – 2
Acids Bases and Salts
Notes
| Acid • Sour in taste. • Turn blue litmus red. • Give H+ ions in aqueous solution. • Aqueous solution conduct electricity. Bases • Bitter in taste. • Turn blue litmus red. • Give OH– ions in aqueous solution. • Does conduct electricity in aqueous solution. |
| Acids & Bases and Salts (i) Physical Properties of Acids (ii) Physical Properties of Bases (iii) Chemical Properties of Acids (iv) Chemical Properties of Bases Reacts with metals to liberate hydrogen. Reacts with metal carbonates/metal hydrogen carbonate to liberate CO2 Reacts with certain metal oxides to form salt and water. |
| Salts When acid and base are combined under the given condition Salt is formed. • Alkali reacts with metal to liberate H2 • Bases reacts with acidic oxides to form water. Classification of Acid, Bases and Salts on the basis of pH scale. |
| pH scale H+ ion concentration of the solution.  |
| Some Common Salts – Common salt = NaCl Sodium hydroxide = NaCl + 2H2O → NaOH + Cl2 + H2 Bleaching Powder = Ca(OH)2 + Cl2 → CaOCl2 + H2O Baking Soda = NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 Washing Soda = Na2CO3 + 10.H2O → Na2CO3.10H2O Plaster of Paris = CaSO4.2H2O 373k heat → CaSO4.1/2 H2O + 1×1/2 H2O Gypsum = CaSO4.1/2 H2O + 1×1/2 H2O → CaSO4.2H2O |
| Understanding Session Acids – The term ‘acid’ has been derived from the Latin word, acidus, which means sour. These are the substances which have sour taste. They turn blue litmus solution red. They give H+ ions in aqueous solution. Classification of Acids Strong Acids = HCI, H2SO4, HNO3 Weak Acids = CH3COOH, Oxalic acid, Lactic acid Concentrated Acid = Having more amount of acid + less amount of water Dilute Acid = Having more amount of water + less amount of acid |
| Bases – These are the substances which are bitter in taste and soapy in touch. They turn red litmus solution blue. They give OH– ions in aqueous solution. Classification of Bases Strong Bases= NaOH, KOH, Ca(OH)2 Weak Bases= NH4OH |
| Alkalis – These are bases which are soluble in water. Examples- NaOH, KOH, Ca(OH)2 |
| Salts – These are the compounds formed from reaction of acid and base. Examples- NaCl, KCl, CaCo3, NaHCo3 |
| Indicators – These are the substances which change their colour/smell in different types of substances. Examples Red cabbage juice – Its colour is Red. (i) When it is tested in Acidic medium it is remains same. (ii) When it is tested in basic medium it is turns Red to green. Turmeric solution – It is a yellow dye Solution. (i) When it is tested in Acidic medium it is remains same. (ii) When it is tested in basic medium it is turns Yellow to Brown. |
| Types of Indicator (1) Natural Indicator (2) Synthetic Indicator (3) Olfactory Indicator |
(1) Natural Indicator
| Found in nature Plant. For Example: Litmus, Red cabbage leaf extract, Flower of hydrangea plant, Turmeric
|
(2) Synthetic Indicator
| These are Chemical Substances. For Example: Phenolphthalein, Methyl orange
|
(3) Olfactory Indicator
| These Substances have different odour in acid and bases. For Example: Onion, Vanilla essence, Clove oil
|
| Chemical Properties Of Acids And Bases Reaction of Metals with Acids and Bases Reaction of Metal Carbonates/Metal Hydrogen Carbonates with Acids and Bases Reaction of Acids and Bases With Each Other Reaction of Metallic Oxides with Acids and Bases |
| 1 . Reaction of Metals with Acids and Bases Reaction of Metals with Acids = Acid + Metal → Salt + Hydrogen gas Example- 2HCl + Zn → ZnCl2 + H2 Reaction of Metals with Bases = Base + Metal → Salt + Hydrogen gas Example- 2NaOH + Zn → Na2ZnO2 + H2↑ Sodium zincate = Na2ZnO2 Hydrogen gas released can be tested by bringing burning candle near gas bubbles, it burns with pop sound. |
| 2. Reaction of Metal Carbonates/Metal Hydrogen Carbonates with Acids = Acid + Metal Carbonate/ Metal Hydrogen Carbonate → Salt + CO2 + H2O Example: (i) 2HCl + Na2CO3 → 2NaCl + CO2 + H2O (ii) HCl + NaHCO3 → NaCl + CO2 + H2O Reaction of Metal Carbonates/Metal Hydrogen Carbonates with Bases = Base + Metal Carbonate/ Metal Hydrogen Carbonate → No Reaction Example: CO2 can be tested by passing it through lime water. (i) Ca(OH)2 + CO2 → CaCO3 (insoluble) + H2O (Lime water turns milky) (ii) When excess CO2 is passed it through lime Stone CaCO3 + CO2 + H2O → Ca(HCO3)2 (Soluble) (Milkiness disappears) |
| 3. Reaction of Acids and Bases With Each Other = Acid + Base → Salt + H2O Neutralisation Reaction – Reaction of acid with base to give salt and water is called as Neutralisation reaction. Example – HCl + NaOH → NaCl + H2O (i) Strong Acid + Weak Base → Acidic salt + H2O [pH of the Solution is less than 7] (ii) Weak Acid + Strong Base → Basic salt + H2O [pH of the Solution is more than 7] (iii) Strong Acid + Strong Base → Neutral salt + H2O [pH of the Solution is = 7] (iv) Weak Acid + Weak Base → Neutral salt + H2O [pH of the Solution is = 7] |
| 4. Reaction of Metallic Oxides with Acids and Bases Reaction of Metallic Oxides with Acids = Metallic Oxide + Acid → Salt + H2O Example: CaO + 2HCl → CaCl2 + H2O Reaction of Metallic Oxides with Bases = Metallic oxides are basic in nature. Example: CaO, MgO are basic oxides. Reaction of Non-metalic Oxides with Bases (i) Non-metallic oxides are acidic in nature. (ii) Non-metalic Oxide + Base → Salt + H20 CO2 + Ca(OH)2 → CaCO3 + H2O |
| Reaction of Acid Acid + Metal Carbonate → Salt + CO2 + Water Acid + Metal → Salt + H2 Acid + Metal Hydrogen Carbonate → Salt + CO2 + H2O Acid + Metal oxide → Salt + H2O Acid + Base → Salt + H2O Reaction of Base Base + Metal → Salt + H2 Base + Metal Carbonate → No Reaction Base + Metal Hydrogen Carbonate → No Reaction Base + Acid → Salt + H2O Base + Non Metallic oxide → Salt + H2O |
| What do all Acids and Bases have in common All acids have H+ ions in common. Acids produce H+ ions in solution which are responsible for their acidic properties. All bases have OH– (hydroxyl ions) in common. All Acids → H+ ions Release All Bases → OH– ions Release |
| Acid or Base in Water Solution (a) Acids produce H+ ions in presence of water. H+ ions cannot exist alone, they exist as H3O+ (hydronium ions). Example : (i) H+ + H2O → H3O+ (ii) HCl + H2O → H3O+ CI– (b) Bases when dissolved in water gives OH– ions. NaOH H2O → Na+ + OH– Mg(OH)2 H2O → Mg2+ + 20H– (i) Bases soluble in water are called alkali. (ii) While diluting acids, it is recommended that the acid should be added to water and not water to acid because the process of dissolving an acid or a base in water is highly exothermic.   If water is added to acid, the heat generated may cause the mixture to splash out and cause burns and the glass container may also break due to excessive local heating. Adding water to acid may be (1) Cause mixture to splash out (2) Break the glass container Mixing an acid or a base with H2O results in decrease of concentration of ions (H3O+/OH-) per unit volume. Such a process is called as dilution. |
| Strength of Acid and Base Strength of acid or base can be estimated using universal indicator. Universal indicator: is a mixture of several indicators. It shows different colours at different concentrations of H+ ions in the solution. pH Scale: A scale for measuring H+ ion concentration in a solution. p in pH stands for ‘potenz’ a German word which means power. 1. pH = 7 → neutral solution 2. pH less than 7 → acidic solution 3. pH more than 7 → basic solution   (i) On diluting an acid : pH increases ↑ (ii) On diluting a base : pH decreases ↓  |
| Importance of pH in everyday life 1. Plants and animals are pH sensitive 2. pH of the soil 3. pH in our digestive system 4. pH change as cause of tooth decay 5. Self defence by animals and plants through chemical warfare |
| 1. Plants and animals are pH sensitive (a) Our body works within the pH range of 7-7 or 8. (b) When pH of rain water is less than 5.6, it is called acid rain |
| 2. pH of the soil Plants require a specific pH range for their healthy growth. |
| 3. pH in our digestive system (a) Our stomach produces HCl acid which helps in digestion. (b) During indigestion, stomach produces more acid and cause pain and irritation. (c) To get rid of this pain, people uses antacid (mild base) like milk of magnesia [Mg(OH)2] to neutralize excess acid. |
| 4. pH change as cause of tooth decay (a) Tooth decay starts when pH of mouth is lower than 5.5. (b) Tooth enamel made up of calcium phosphate (hardest substance in body) does not dissolve in water but corrodes when pH is lower than 5.5 due to acids produced by degradation of food particles by bacteria. (c) Using toothpaste (generally basic) tooth decay can be prevented. |
| 5. Self defence by animals and plants through chemical warfare (a) Bee sting leaves an acid which cause pain and irritation. Use of a mild base like baking soda on stung area gives relief. (b) Stinging hair of nettle leaves inject methanoic acid causing burning sensation or pain. Rubbing with leaf of dock plant give relief. |
| pH of Salts (i) Strong Acid + Strong Base → Neutral Salt: pH = 7 Example: NaCl (ii) Salt of strong acid + Weak base → Acidic salt: pH < 7 Example: NHCI (iii) Salt of strong base + Weak acid → Basic salt: pH > 7 Example: CH3COONa |
| Chemicals Form Common Salts (NaCl) Common salt= NaCl Sodium hydroxide= NaCl + 2H2O → NaOH + Cl2 + H2 Bleaching Powder= Ca(OH)2 + Cl2 → CaOCl2 + H2O Baking Soda= NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 Washing Soda= Na2CO3 + 10.H2O → Na2CO3.10H2O Plaster of Paris= CaSO4.2H2O 373k heat → CaSO4.1/2 H2O + 1×1/2 H2O Gypsum= CaSO4.1/2 H2O + 1×1/2 H2O → CaSO4.2H2O |
| 1. Sodium Hydroxide (NaOH) When electricity is passed through an aqueous solution of NaCl (brine), it decompose to form NaOH. (Chlor-alkali process)  2NaCl + 2H20 → 2NaOH + Cl2 + H2 At anode : Cl2 gas At cathode: H2 gas Near cathode: NaOH solution is formed. Uses of Substances: H2: Fuels, margarine Cl2: Water treatment, PVC, CFC’s HCI: Cleaning steels, medicines NaOH: Degreasing metals, soaps and paper making Bleach (Cl2 + NaOH): Household bleaches, bleaching fabrics |
| 2. Bleaching Powder (CaOCl2) It is produced by the action of chlorine on dry slaked lime. Cl2 + Ca(OH)2 → CaOCl2 + H2O Uses: (a) Bleaching cotton and linen in textile industry. (b) Bleaching wood pulp in paper factories. (c) Oxidizing agent in chemical industries. (d) Disinfecting drinking water. |
| 3. Baking Soda (Sodium Hydrogen Carbonate) (NaHCO3) NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 (Baking soda) • It is mild non-corrosive base. • When it is heated during cooking: 2NaHCO3 Δ → Na2CO3 + H2O + CO₂ Uses (a) For making baking powder (mixture of baking soda and tartaric acid). When baking powder is heated or mixed with water, CO2 is produced which causes bread and cake to rise making them soft and spongy. (b) An ingredient in antacid. (c) Used in soda-acids, fire extinguishers. |
| 4. Washing Soda (Na2CO3.10H2O) Recrystallization of sodium carbonate gives washing soda. It is a basic salt. Na2CO3 + 10H2O→ Na2CO3.10H2O Uses (a) In glass, soap and paper industry. (b) Manufacture of borax. (c) Cleaning agent for domestic purposes. (d) For removing permanent hardness of water. |
| 5. Plaster of Paris (Calcium sulphate hemihydrates) (CaSO4.1/2H2O): On heating gypsum (CaSO4.2H2O) at 373K, it loses water molecules and becomes Plaster of Paris (POP). It is a white powder and on mixing with water it changes to gypsum. = CaSO4.1/2H2O + 1×1/2H2O → CaSO4.2H2O Uses (a) Doctors use POP for supporting fractured bones. (b) For making toys, material for decoration. (c) For making surfaces smooth. |
| Water of Crystallization It is a fixed number of water molecules present in one formula unit of a salt. Examples- CuSO4.5H2O has 5 water molecules. Na2CO3.10H2O has 10 water molecules. CaSO4.2H2O has 2 water molecules. |
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