Acids, Bases and Salts Class - 10th

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1. Acids, Bases and Salts Class – 10 th

2. What is an Acid? A substance that tastes sour, turns Blue Litmus Red , and neutralizes bases is known as an Acid . {pH – Less Than 7 } They can be classified in two categories on the basis of their strength: Weak Acids – It is an acid that Dissociates Incompletely , releasing only some of its hydrogen atoms into the solution. For e.g.:- , , etc . Strong Acids – It is an acid that is Completely Dissociated in an aqueous solution. For e.g.:- HCl, , etc.  

3. What is a Base? A substance bitter in taste, turns Red Litmus Blue , and neutralizes acid is known as a Base . They are generally soapy in touch. {pH – More Than 7 } They can be classified in two categories on the basis of their strength: Weak Base – They are the basic substances that Dissociates Incompletely in water. For e.g.:- , , etc. Strong Base – They are the basic substances that Completely Dissociates in water. For e.g.:- NaOH, KOH, etc.  

4. Physical Properties of Acids & Bases Properties Acids Bases Color Mineral acids are colorless. Organic acids are white-colored solids. Bases are colorless except for the hydroxides of Fe & Cu. Taste Sour Bitter Touch – Slippery Solubility Soluble in water. Some bases are soluble which are called Alkalis .

5. Chemical Properties of Acids & Bases

6. Acids & Bases with Metals The Metal in this reaction displaces Hydrogen atoms from the acids as H 2 gas and forms a compound called a Salt . Mg(s)+2HCl(aq.)⟶MgCl 2 (aq)+H 2 (g) Alkalis (bases that are soluble in water) react with metals to produce Salt and Hydrogen gas . 2NaOH(a) + Zn(s) → Na 2 ZnO 2 (s) + H 2 (g) Acid + Metal → Salt + Hydrogen gas Bases + Metal → Salt + Hydrogen gas

7. Metal Carbonates/ Bicarbonates with Acids Metal Carbonates/ Bicarbonates react with Acids to produce Salt , Carbon Dioxide and Water . Na 2 CO 3 (s) + 2HCl (aq.) → 2NaCl (aq.) + CO 2 (g) + H 2 O (l) NaHCO 3 (s) + HCl (aq.) → NaCl (aq.) + CO 2 + H 2 O (l) Bases do not react with Metal Carbonates/ Bicarbonates at all. Metal Carbonate / Bicarbonate + Acid → Salt + Carbon dioxide + Water

8. Metal Oxide with Acids Metallic Oxides are Basic in nature, but react with acids to produce Salt and Water . CaO (s) + 2HCl (aq.) → CaCl 2 ​(s) + H 2 O (l) Metal oxide + Acid → Salt + Water

9. Non – Metal Oxide with Bases Non-Metal Oxides are acidic in nature, but reacts with a base to neutralize each other resulting respective Salt and Water are produced. 2NaOH + CO 2 → Na 2 CO 3 + H 2 O Non – Metal Oxide + Base  Salt + Water

10. Neutralization The reaction between an strong acid and strong base to give a salt and water is known as a Neutralization reaction. NaOH(aq) + HCl(aq) → NaCl(aq) + H 2 O(l) Acid + Base → Salt + Water

11. What are Indicators? The Indicators tells whether a substance is acidic or basic by changing their color. Thera are three types of Indicators: Natural Indicators – They are obtained from the nature. For e.g.:- Litmus, Turmeric, etc. Synthetic Indicators – They are synthesized in a laboratory and are artificial. For e.g.:- Methyl Orange, Phenolphthalein, etc. Olfactory Indicators – Their odor changes in acidic or basic media. For e.g.:- Vanilla, Onion, etc.

12. What are Alkalis? An Alkali is a base that dissolves in water. They are soapy to touch, bitter and corrosive. For e.g.:- NaOH, KOH, etc. {pH – More Than 7 } Properties of Alkalis are:- They are soft and have low density. Alkalis have low melting and boiling points. They give characteristic color to the flame. Alkalis react easily with Halogens . They can be stored in mineral oil solutions.

13. Dilution of Acid The process of dissolving an acid or a base in water is a Highly Exothermic . Care must be taken while mixing Conc. Nitric Acid or Sulphuric Acid with water. Acid to Water – The acid must always be added slowly to water with constant stirring. Water to Acid – If water is added to a conc. acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may break due to excessive heat. Mixing an acid or base with water results in decrease in the conc. of ions (H 3 O+/OH– ) per unit volume. Such a process is called Dilution .

14. pH: The Universal Indicator pH Scale was developed to measure the conc. of hydrogen ions in a solution. The p in pH stands for ‘ Potenz ’ in German, meaning ‘ Power ’. The pH scale ranges from ( Very Acidic ) to 14 ( Very Alkaline ). The pH of a neutral solution is 7. Value less than 7 on the scale represent an acidic solution . Value more than 7 on the scale represent an basic solution .

15. pH in Everyday Life Are Plants and Animals pH sensitive? Our body works within the pH range of 7.0 to 7.8 . Living organisms can survive only in a narrow range of pH change. When pH of rain water is Less Than 5.6 , it is called Acid Rain . When acid rain flows into rivers, it lowers the pH of river water. The survival of aquatic life in such rivers become difficult.

16. What should be the pH of Soil in the Backyard? Plants require a specific pH range for their healthy growth. The optimal pH range of the soil suitable for plant growth should vary in-between 5.5 to 7.0 . The soil should neither be alkaline nor acidic in nature to support the growth of plants. Change in pH of the soil affects the availability of nutrients for growth of the plants.

17. What is the pH in our digestive system? Our stomach produces HCl which helps in the digestion of food without harming the stomach. During indigestion, stomach produces too much acid which causes pain and irritation. To get rid of the pain, people use bases called Antacids . To neutralize the excess acid, Magnesium Hydroxide ( Milk Of Magnesia ) is used.

18. Is pH change responsible for Tooth Decay? Tooth Decay starts when the pH of the mouth is lower than 5.5 . Tooth enamel is made up of Calcium Hydroxyapatite (crystalline form of Calcium Phosphate ) is the hardest substance in the body. It is corroded when the pH in the mouth is below 5.5. Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. The best way to prevent this is to clean the mouth using basic toothpastes.

19. Self defense by Animals And Plants through chemical warfare Bee-sting Leaves an acid which causes pain and irritation. Use of a mild base like baking soda on the stung area gives relief. Stinging hair of nettle leaves inject Methanoic Acid ( Formic Acid ) causing burning pain.

20. Natural Source Acids Vinegar Acetic Acid Orange Citric Acid Tamarind Tartaric Acid Tomato Oxalic Acid Curd Lactic Acid Lemon Citric Acid Ant-sting Methanoic Acid Nettle-sting Methanoic Acid Some naturally occurring acids:-

21. What is a Salt? The substance formed (in addition to water) when acid and base react with each other is called Salt . They generally show neutral behavior. {pH – 7 } They can be classified in 2 types: Acidic Salt – They are formed by the Partial Replacement of Hydrogen Ions of an acid by a metal. For e.g.:- NH 4 Cl, FeCl 3 , etc . Basic Salt –They are formed by the Partial Replacement of Hydroxide Ions of a base with an acid. For e.g.:- , , etc .  

22. Properties of Salts

23. Common Salt Chemical Name :- Sodium Chloride Chemical Formula :- NaCl Preparation :- It is formed by the combination of HCl and Sodium Hydroxide . HCl + NaOH → NaCl + H 2 O Uses :- It is widely used in food industries as a food preservative. I t is a major raw material in the industrial manufacturing of various chemicals such as sodium carbonate, sodium hydrogen carbonate etc.

24. Caustic Soda Chemical Name :- Sodium Hydroxide Chemical Formula :- NaOH Preparation :- When electricity is passed through an aq. solution of NaCl ( Brine ), it decomposes to form NaOH. This process is also called Chlor – Alkali process. 2NaCl + 2H 2 O → 2NaOH + Cl 2 + H 2 Uses :- It is used for the making of soaps and detergents, paper and fibers. It is also used for de-greasing metals.

25. Bleaching Powder Chemical Name :- Calcium Oxychloride Chemical Formula :- CaOCl 2 Preparation :- It is formed by the action of Chlorine on Ca(OH) 2 . Ca(OH) 2 + Cl 2 → CaOCl 2 + H 2 O Uses :- It is used to make drinking water germ free. It is also used as an oxidizing agent in many industries.

26. Baking Soda Chemical Name :- Sodium Hydrogencarbonate Chemical Formula :- NaHCO 3 Preparation :- It is formed when NaCl reacts with Ammonia, water and CO 2 . NaCl + H 2 O + NH 3 + CO 2 → NaHCO 3 + NH 4 Cl Uses :- The baking soda is used in the kitchen for making crispy pakoras. It is also used in soda-acid fire extinguishers.

27. Washing Soda Chemical Name :- Sodium Carbonate Decahydrate Chemical Formula :- Na 2 CO 3 .10H 2 O Preparation :- It is formed when 10 water molecules are added to Na 2 CO 3 . Na 2 CO 3 + 10H 2 O → Na 2 CO 3 .10H 2 O Uses :- It is used for removing permanent hardness of water. It can be used as a cleaning agent for domestic purposes.

28. Plaster Of Paris Chemical Name :- Calcium Sulphate Hemihydrate Chemical Formula :- CaSO 4 . ½ H 2 O Preparation :- It is formed when Gypsum is heated at 373 K (100 C) , to lose water. CaSO 4 . 2H 2 O → CaSO 4 . ½ H 2 O + 3/2 H 2 O Uses :- It is used by doctors to support the fractured bones. It is used for making toys, materials for decoration and for making surfaces smooth.

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