Siva Prasad is teaching live on Unacademy Plus
Class X - NCERT Science Summany Part-1 SIVA PRASAD
About Me . Bachelors and Masters in Physics from Indian Institute of Science (ISc), Bangalore .INSPIRE Scholar, DST Govt. of India Interested in Physics, current affairs, economics.... . Physicist, Blogger, Teacher.... Wrote UPSC CSE Mains 2017 Research Publication in Journal of Applied Physics
Acids . Sour in taste Litmus test - gives red colour Turmeric - yellow Phenolphthalein - Colorless
Bases . Soapy feeling when rubbed . Bitter taste Litmus test - blue colour Turmeric red Phenolphthalein - Pink Bases soluble in water are called- Alkali
Strength of Acid/Base . A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed . The p in pH stands for 'potenz' in German, meaning power. Ve alkaline) pH should be thought of simply as a number which indicates the acidic or basic nature of a solution .Higher the hydronium ion concentration, lower is the pH value.
Strength of Acid/Base The pH of a neutral solution is 7. Values less than 7 on the pH scale represent an acidic solution. . As the pH value increases from 7 to 14, it represents an increase in OH ion concentration in the solution, that is, increase in the strength of alkali. Neutral Acidic nature increasing Basic nature increasing 0 14 OH Increase in H on concentration Decrease in H Figure 2.6 Variation of pH with the change in concentration ofH(aq) and OH (aq) ions
pH Scale 0 2 3 5 6 7 8 9 10 11 12 13 14 Sodium hydroxide solution (about 14) Gastric Milk of juice about 1.2) Lemon juice (about 2.2) Pure water blood 7.4) (10) ide)
pH in everyday life . 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. . Acid rain - pH less than 5.6 . Digestive system our stomach produces hydrochloric acid. It helps in the digestion of food without harming the stomach. During indigestion the stomach produces too much acid and this causes pain and irritation. To get rid of this pain, people use bases called antacids. These antacids neutralise the excess acid. Magnesium hydroxide (Milk of magnesia), a mild base, is often used for this purpose.
pH in everyday life . Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up of calcium phosphate, is the hardest substance in the body. It does not dissolve in water, but is corroded when the pH ir 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. . Using toothpastes, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.
Naturally occurring acids Table 2.3 Some naturally occurring acids Natural source Aetd Vinegar Orange Tamarind Tomato Acetic acicd Citric acid Tartaric acid Oxalic acid Natural source Sour milk (Curd) Lemon Ant sting Nettle sting Acid Lactic acid Citric acid Methanoic acid Methanoic acid
Bleaching Powder Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)]. Bleaching powder is represented as CaOCl2. Bleaching powder is used - . () for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry; (ii) as an oxidising agent in many chemical industries; and . . (ii) for disinfecting drinking water to make it free of germs. Ca(OH), + Cl, CaOCl, + H,0
Washing Soda . Na2CO3.10H2O Uses of washing soda (0) Sodium carbonate (washing soda) is used in glass, soap and paper industries (i) It is used in the manufacture of sodium compounds such as borax (ii)i Sodium carbonate can be used as a cleaning agent for domestic purposes. (iv) It is used for removing permanent hardness of water.