[Music] [Applause] [Music] foreign acids or the chemical compounds that are sore in taste acids are present in many things that we use in our daily life curd has lactic acid lemon has citric acid and vinegar has acetic acid in it bases are the chemical compounds that are bitter to taste and soapy to touch bases are present in detergents toothpaste and hair dyes then how do we test the presence of acid and bases we can test the presence of acid or base using acid base indicators litmus is the most popular acid base indicator it is a natural acid-base indicator obtained from a kind of lichens blue litmus paper turns to red when dipped in acid red litmus paper turns to Blue when dipped in a base red cabbage turmeric and hibiscus are some examples of natural indicators methyl orange and phenolphthalein these are synthetic acid-base indicators when methyl orange is added to an acid it turns to red color if it is added to your base its color changes to Yellow when phenolphthalein added to an acid there is no color change observed but if it is added to a base its color changes to Pink here we have some chemical compounds let us test these compounds with acid base indicators among these compounds HCL h2so4 hno3 and ch3cooh they turns the blue litmus to red when methyl orange added they produce red color and remains colorless with phenolphthalein this indicates that all these compounds are acids the remaining compounds like sodium hydroxide calcium hydroxide potassium hydroxide magnesium hydroxide and ammonium hydroxide they turns the red litmus to Blue and produces an yellow color with methyl orange they form pink color when phenolphthalein is added this proves that they are all bases certain acid base indicators works with smell these kind of acid base indicators are called olfactory indicators examples onion vanilla Essence and clove oil using onions as acid-base indicators first let us take a polythene cover and place some chopped onions in it place a small piece of cloth in the same cover along with onions now tie the cover using a thread or tape place this packet in the refrigerator for the whole night on the next morning take out the cloth from the cover cut two strips from the cloth as shown now smell these two strips of cloth you will get onion smell from both the strips now place these strips on a flat surface and add dilute HCL drops to strip one and sodium hydroxide drops to strip too rinse these two strips in distilled water separately if you know why we need to rinse them in distilled water at this step please write it in the comment section now once again smell the two strips the strip to which HCL is added gives the same onion smell but the strip to which sodium hydroxide is added do not give any onion smell it has lost its onion smell do you know why the onion treated cloth strips become acidic since the vapors from the onions are acidic when this acidic cloth strip is treated with HCL there is no reaction between HCL and onion cloth whereas in the other strip that is treated with sodium hydroxide there is an acid-based reaction between the sodium hydroxide and onion treated cloth strip here the neutralization reaction takes place so the cloth strip loses its order a reaction of acids and bases with Metals first let us see the reaction between an acid and a metal add few zinc granules to a 5 ml dilute h2so4 they both react and forms a salt called as zinc sulfate and hydrogen gas so acid plus metal gives rise to Salt plus hydrogen gas now let us see the reaction between a base and a metal add few zinc granules to 5 ml of concentrated sodium hydroxide and warm the contents using a burner they both react and forms a salt called sodium zincate and hydrogen gas so base plus metal cubes rise to Salt plus hydrogen gas but all metals may not react with the bases in the same way reaction of metal carbonates with acids take 0.5 grams of metal carbonate like sodium carbonate and add 2 ml of diluted CL it forms a salt that is sodium chloride water and gas this gas when passed through calcium hydroxide solution it forms a white precipitate that is calcium carbonate we know that when calcium hydroxide reacts with carbon dioxide it turns into calcium carbonate that means here the gas produced in this reaction is carbon dioxide so when a metal carbonate reacts with an acid it gives rise to Salt plus water plus carbon dioxide reaction of metal hydrogen carbonates with acids take 0.5 grams of metal hydrogen carbonate like sodium hydrogen carbonate and add 2 ml of dilute HCL it forms a salt that is sodium chloride and water and a gas the gas produced in this reaction is also carbon dioxide so when a metal hydrogen carbonate reacts with an acid it gives rise to salt water plus carbon dioxide so all metal carbonates and metal hydrogen carbonates react with acids and Produce Salt carbon dioxide and water reaction between acids and bases Take 2 ml of dilute sodium hydroxide and add two drops of phenolphthalein to it since sodium hydroxide is the base we phenolphthalein turns into pink color now add few drops of HCL the solution becomes acidic and the pink color disappears now again add a few drops of sodium hydroxide the pink color reappears in this experiment we have seen that by adding an acid to the base we can reduce or completely remove the basic nature of the substance in the same way by adding base to an acid we can reduce or completely remove the acidic nature of this substance this type of reactions are called neutralization reactions so when a base is added to an acid it gives rise to a salt and water reaction of metal oxides with acids take a small amount of copper oxide in a beaker and add dilute HCL Slowly by stirring the color of the solution slowly changes to bluish green color copper oxide reacts with HCL and forms copper chloride and water so when a metal oxide reacts with acid it forms salt plus water reaction of non-metalloxide lights with base calcium hydroxide is a base when it is treated with a non-metallic oxide like carbon dioxide it forms a white precipitate called calcium carbonate a salt so when a base is treated with a non-metallic oxide it produces salt plus water the common thing in both acids and bases take some dilute HCL in a beaker and fix two electrodes now take two wires now connect one bulb as shown in the picture now connect the free ends of the wires to your power source the current flows through the solution and the bulb glows replace the contents in the beaker with glucose solution the bulb does not glow replace the content of the beaker with alcohol the bulb does not glow now again replace with sodium hydroxide the bulb glows this shows that the bulb glows only in case of acids and bases that means that acids and bases they conduct electricity do you know why acids and bases when dissolved in water they produce cations that means positive ions and anions that are negative ions when HCL is dissolved in water it produces cations as h plus ions and anions as CL minus ions these hydrogen ions cannot exist alone they exist in the form of hydronium ions in the same way if we dissolve sodium hydroxide in water it forms any plus cations and o h minus anions so the common thing among acids and bases is that they both produce ions in water and conducts electricity dilution if we mix an acid or base with water it results in the decrease in the concentration of ions per unit volume this process is called dilution dilution is a highly exothermic reaction that means when we add an acid or a base to water large amounts of heat is released so always add acid to water Slowly by stirring never add water to acid if water is added to acids it splashes out a can cause Burns due to local heating strength of acids and bases all acids do not have same strength in the same way all bases do not have the same strength we can know the strength of an acid or a base using pH scale it has values from 0 to 14. the substances with ph 7 are neutral the substances with ph below 7 are acidic and above 7 are basic the acids that are closer to zero are strong acids and closer to 7 are weak acids the bases that are closer to 14 are strong bases and that are closer to 7 or weak basis importance of pH in daily life the pH of water in water bodies is very important for Aquatic Life acid rains make the water bodies acidic which causes a great damage to the water plants and animals plants need a specific pH for their Healthy Growth Farmers test the pH of the soil from time to time to add necessary chemicals to ensure the proper growth of plants importance of pH in our body our stomach produces hydrochloric acid that helps in the digestion of proteins if more acid is produced in our stomach it leads to a condition called acidity to reduce stomach acidity bases like magnesium hydroxide are used as antacids the tooth enamel which is made up of calcium hydroxyapatite which is dissolved by the acid produced in the mouth the bacteria in the mouth feeds on the sugars and produces acids which reduce the mouth pH below 5.5 this causes tooth decay acids and bases in self-defense living things use acid bases for their defense beasting has an acid which cause pain and irritation as a remedy we can use a base like baking soda on it natural Leaf sting also has acid and causes rash and pain its acidic effect can be neutralized by rubbing with a dog plant now let us know about salts what is the pH of salts or salts neutral acidic or basic some salts are neutral some are acidic and some salts are basic in nature salts of strong acid and strong base are neutral with ph value of 7. salts of strong acid and weak base are acidic with ph value less than 7. salts of weak acid and strong base are basic in nature with ph value more than 7. now let us learn about the important salt that is sodium chloride since it is used in our day-to-day life it is also called as common salt but do you know that it is the main ingredient in making many useful chemical compounds sodium chloride is used to make caustic soda baking soda washing soda and bleaching powder sodium hydroxide NaOH manufacture of sodium hydroxide when electricity is passed through an aqueous solution of sodium chloride it produces three products that are sodium hydroxide chlorine gas and hydrogen gas this process is called as Chlor Alkali process in this setup chlorine gas is produced at the anode side and the hydrogen gas is released at the cathode side sodium hydroxide is formed at the cathode uses of the products formed in Chlor Alkali process the chlorine gas produced in this reaction can be used for water treatment swimming pools manufacture of PVC in making disinfectants and in making of chlorofluorocarbons and pesticides the hydrogen gas produced in this reaction can be used as a fuel and also in making of margarine and fertilizers the sodium hydroxide produced in this reaction is used in decreasing Metals it is also used in making of soaps detergents paper and artificial fibers baking soda nah CO3 manufacture of baking soda when common salt is treated with water carbon dioxide and ammonia it gives ammonium chloride and baking soda uses of baking soda it is used as a cooking ingredient it is also used as an antacid to reduce the stomach acidity it is also used in certain types of fire extinguishers do you know why baking soda is added to food items when baking soda added foods are cooked the sodium hydrogen carbonate becomes sodium carbonate plus water plus carbon dioxide this carbon dioxide Gas makes the food item spongy and fluffy so to make the food spongy and floppy baking soda is added washing soda and A2 CO3 recrystallization of sodium carbonate gives Washing Soda uses of washing soda it is used in the manufacture of glass soap and Paper Industries it is used in the manufacture of borax it is also used as a cleaning agent it helps in the permanent removal of water hardness bleaching powder CAO cl2 manufacture of bleaching powder calcium hydroxide is treated with chlorine gas produced during Chlor Alkali process to prepare bleaching powder uses of bleaching powder it is used in whitening of cloth paper jute and linen fibers in their manufacture it is used in Industries as an oxidizing agent it is also used in disinfecting the white powder that is sprinkled near public toilets and garbage bins is nothing but bleaching powder plaster of Paris CA so4 1 by 2 H2O manufacture of plaster of Paris on heating gypsum at 373 kelvins it loses water molecules and become calcium sulphate hemihydrates it is called as plaster of Paris do you know why it is called as plaster of Paris in 18th century extensive mining of gypsum was started in Paris for the large-scale production of plaster since then it's being called as plaster of Paris uses of plaster of Paris it is used by doctors as plaster to support the broken bones it is also used to make toys and models this is all about the acids bases and salts thanks for 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