ACIDS,BASES&SALTS FOR CLASS X CBSE -MURALIDAR.N.K.JANAKI

1. Acids, Bases & Salts Muralidar.N.K.Janaki

2. CHEMICAL REACTIONS • Chemical Reactions are associated with chemical change. • Whenever a chemical change occurs chemical reaction is said to take place. • Chemical reactions are usually irreversible and a new product is formed. we are surrounded by acids and bases in the world. Most of them are weak.

3. Signs of Chemical Reactions There are five main signs that indicate a chemical reaction has taken place: Change in state Evolution of a gas Change in temperature change in color

4. ACID: Substance that releases H+ ions in aqueous solution BASE: Substance that releases OH- ions in an aqueous solution SALT: Is a compound which is formed by neutralization reaction between an ACID & BASE. Eg:NaCl. • Some substances have an OH, but ARE NOT BASES • CH3OH  does not form OH ions. Why?

5. ACID BASE ARRHENIUS BASE Any substance that provides hydroxide ions, OH-, when dissolved in water. BRØNSTED BASE Any substance capable of accepting a proton from another substance. EXAMPLES OF AN ARRHENIUS BASE KOH is a base: KOH(aq) ------------K+ (aq) + OH- (aq) ARRHENIUS ACID Any substance that provides H ions, H+, when dissolved in water. BRØNSTED ACID Any H-containing substance that is capable of donating a proton (H+) to another substance. EXAMPLES OF AN ARRHENIUS ACID HNO3 is an acid: HNO3(aq) -------- H+ (aq) + NO3- (aq) EXAMPLE OF A BRØNSTED ACID HNO3(aq)+H2O(l) ----H3O+(aq)+NO2-(aq) EXAMPLE OF A BRØNSTED ACID AND BASE HNO3(aq) + H2O(l) H3O+ (aq) + NO2-(aq) In this reaction, HNO2 behaves as a Brønsted acid by donating a proton to the H2O. The H2O behaves as a Brønsted base by accepting the proton.

6. NATURAL SOURCES OF ACIDS NATURAL SOURCES OF ACIDS • Broccoli • Cucumber • Cabbage • Baking soda • Ginger • Green beans • Fruits like – orange, lemon, tamarind etc. • Curd • Olives • Coffee • Mustard Types of AcidsMonoprotic- solution that produces 1 mole of H+ ions per mole of acid HCl, HNO3 Diprotic- solution that produces 2 moles of H+ ions per mole of acid H2SO4 Triprotic-solution that produces 3 moles of H+ ions per mole of acid H3PO4 Polyprotic- 2 or more H+ per mole of acid

7. ACID BASE SALT When the oxide of some non-metals dissolve in water they make an acid. When the oxide of somemetals they make an BASE. • The salt contains the metal atom from the alkali, and part of the acid molecule. • Reaction of salt with water is known as salt hydrolysis Acids donate a proton. Acid is electron pair ACCEPTOR +vecharges are ACID. Bases donate OH ion. Base is electron pair DONOR. -vecharges are BASES. • Hydrolyzing salts usually come from: • Strong acid + Weak base or • Weak acid + Strong base • Strong refers to the degree of ionization • Strong Acid + Strong Base = Neutral Salt How do you know if a chemical is an acid? It usually starts with Hydrogen. HCl, H2SO4, HNO3, etc. • Resulting salt is acidic or basic, check the “parent” acid and base that formed it. Practice on these: • HCl + NaOH---NaCl(neutral salt) • H2SO4 + NH4OH (NH4)2SO4, acidic salt • CH3COOH + KOH CH3COOK basic salt • Acid rain to eat away at sculptures • Framed paintings to be damaged • Ants and bees use it to sting

8. ACID BASE SALT BITTER TASTE CORROSIVE (Strong base), SOAPY, SLIPPERY. • SALT is used for ionic compounds - is composed of +velycharged cations (usually metal or ammonium ions) & -velycharged anions, so that the product remains neutral & without a net charge. • Anions may be inorganic (Cl-) as well as organic (CH3COO-) & monoatomic (F-) as well as polyatomic ions (SO42-) SOUR TASTE CORROSIVE Litmus solution red & turn blue litmus paper red. Basic solution litmus from red to blue. pH >7. pH 7-14. Lower –Weak , Higher-Stronger . pH <7ie., pH 1-6. Lower –stronger, Higher-weaker . • Salt's solution in water is called electrolytes. • Salts with OH- are basic salts (CaOHCl, BaOHNO3) & with H+ are acidic salts (NaHSO4) • Taste - differs from salt to salt. It can elicit all the five basic tastes, like salty(NaCl), sweet(Pbdiacetate very toxic), sour(k bitartrate), bitter (MgSO4), & umami or savory (MSG). Substance releases OH- ions in aqs. Solution. Bases contain OH- ions. • Dissolve in water to produce particles called hydrogen ions. producing H3O+ ions when dissolved in water. OH- Able to conduct electricity

9. ACID BASE SALT Acids dissociates when dissolved in water.(turn from molecule into ions). Acids Classified as strong or weak depending on its ability to dissociate in water. Strong Acid dissociates completely in water. E.gH2SO4,HNO3. Weak Acid dissociates partially in water e.g Acetic acid • At room temperature, salts are solid crystalline ionic compounds that contain the cation (+ve ion) of a base & anion (-ve ion) of an acid in their formulas. Hydroxides of Group-1 & Group-2 Metals are STRONG. All others are WEAK Bases also react with fats and oils and convert them into smaller, soluble molecules. • NaCl: contains 1 Na+cation from base NaOH, & 1 Cl- anion from the acid HCl. Most household cleaning products contain basic substances(e.g.lye (NaOH) in drain cleaner & Ammonia in liquid household cleaners) • NaNO3 :contains 1 Na+cation from base NaOH, & 1 NO3- anion from acid HNO3 • Na2SO4 :contains 2Na+cations from base NaOH, & 1 SO42- from acid H2SO4. • All acids undergo characteristic double-replacement reactions with solid oxides, hydroxides, carbonates, & bicarbonates. • Cationof a salt can be any positive ion, except H+, & it will usually be a simple metal ion or NH4+. Base react readily with acid is called a neutralization reaction

10. TYPES OF ACID Weak Acids do not ionize completely: All Organic Acids (Acetic, formic, etc), Boric, Nitrous, Phosphoric, Sulfurous Strong Acids ionize completely: HCl, HI, H2SO4 & HNO3 MINERAL ACID (INORGANIC ACID) Acids prepared from the minerals of the earth are called mineral acids. These are man made acids. Common mineral acids are HCl, H2SO4 & HNO3. Conc. Mineral acids are very dangerous. They can burn hands & Clothes. ORGANIC ACID Acids Present in plant and animals are called Organic acids. Organic acids are naturally occurring acids. Eg: Acetic acid, Citric Acid, Tartaric acid, Lactic Acid, Oxalic acid and Formic acid. ACIDS ARE INORGANIC AND ORGANIC. ACIDS ARE WEAK AND STRONG

11. ORGANIC ACIDS • Formic acid is present in bees, ants & other stinging insects • When an ant bites.. It injects acidic liquid (formic acid) into the skin the effect of the acid can be neutralised by rubbing moist baking soda or calamine solution, which contains zinc carbonate. • Citric acid makes lemon sour. • It is a very good antioxidant & therefore helps in improving the health of our skin… . & it helps in quick healing. • Tartaric acid is present in grapes and is therefore present in wine made by grapes too… • Lactic acid is a consequent of sour milk and yogurt. • It is also formed in muscles during exercise. • It is responsible for tiredness and muscle pain… • Acetic acid is used as a preservative. • It is also called ethanoic acid. • Carbonic acid is usually present in fizzy drinks.

12. ACID RAIN • Acid rain is a rain or any other form of precipitation that is unusually acidic. • It can have harmful effects on plants, aquatic animals, and infrastructure (especially structures made of marble).

13. Reaction of ACIDS: • Reaction with metals: • The reaction between metals and acids produce salts and hydrogen gas. • Acid + Metal -------------- Salt + Hydrogen • A lighted splint is used to test for the presence of hydrogen gas. It extinguishes the splint and gives a “pop” sound. • Reaction with carbonates: • Acid react with carbonate compounds to produce salts, carbon dioxide and water. • Acid + Carbonate ------------ Salt + Carbon Dioxide + Water • Limewater is used to test for the presence of carbon dioxide gas. The limewater turns chalky when carbon dioxide is bubbled into it. • Reaction with Alkalis: • Acid react with alkalis to produce salts and water only • Reaction between acids & alkalis is called NEUTRALISATION reaction. • Acid + Alkalis ------------------ Salt + Water • Universal indicator can be used to show that the solution has become neutral after the reaction. It gives a pale green color in neutral solutions.

14. Neutralization HCl + NaOH → H2O + NaCl acid base water salt Double Replacement

15. Reactions with BASE: • Reaction with metals: • The reaction between metals and Base produce salts and hydrogen gas. • Base + Metal -------------- Salt + Hydrogen • Reaction with Non Metallic oxide: • Acid react with Non metallic oxide to produce salts & water. • Acid + Carbonate ------------ Salt + Water • CuO + 2HCl CuCl2 + H2O • Reaction with Alkalis: • Acid react with alkalis to produce salts and water only • Reaction between acids & alkalis is called NEUTRALISATION reaction. • Acid + Base (Alkalis ) ------------------ Salt + Water • Universal indicator can be used to show that the solution has become neutral after the reaction. It gives a pale green color in neutral solutions.

16. All the metal do not react with base to form salts & hydrogen gas Weak Bases: ammonia; potassium carbonate, sodium carbonate, organic amines. Strong Bases: sodium hydroxide; sodium phosphate; barium hydroxide; calcium hydroxide

17. ACID BASE SALT

18. ACIDS, BASES & SALTS REACTIONWITH ACID BASE METAL + ACID SALT + H2 Zn + H2SO4 ZnSO4 + H2 METAL+ BASE SALT+ H2 Zn + NaOH Na2ZnO3+ H2 METALS METAL CARBONATE/ METAL HYDROGEN CARBONATE METAL CARBONATE+ ACIDSALT + CO2+ H2O Na2CO3 + HClNaCl +CO2+H2O METAL HYDROGEN CARBONATE+ ACIDSALT + CO2+ H2O NaHCO3+ HClNaCl+CO2+ H2O METAL OXIDE +ACIDSALT + H2O CuO + 2HCl CuCl2 + H2O METALLIC OXIDE EACH OTHER ACID + BASE SALT + H2O HCl + NaOH NaCl2 + H2O BASE + ACID SALT + H2O NaOH+ HCl NaCl2 + H2O NON METAL OXIDE + BASESALT + H2O CuO + 2HCl CuCl2 + H2O NON-METALLIC OXIDE

19. SALT H2O METALLIC OXIDE H2O SALT SALT ACID BASE METAL H2 METALLIC CARBONATES SALT CO2 H2O

20. SALT H2O METALLIC OXIDE H2O SALT SALT ACID BASE METAL H2 METALLIC CARBONATES ACID TO WATER TO DILUTE. NOT WATER TO ACID - IT SPLASH SALT CO2 H2O

21. SALT H2O NON-METALLIC OXIDE BASE ACID SALT METAL SALT H2 H2O BASES SOLUBLE IN WATER IS CALLED AS ALKALI

22. SALT H2O NON-METALLIC OXIDE BASE ACID SALT METAL SALT H2O H2 BASES SOLUBLE IN WATER IS CALLED AS ALKALI

23. Aqs. Soln. SALT (Brine) Chloralkali process H2O+CO2+NH3 electricity H2 NaOH Cl2 Baking Soda (NaHCO3) NH4Cl Ca(OH)2 Bleaching powder Tartaric acid Washing Soda Na2CO3 Baking powder

24. SALT: compound which is formed by neutralization reaction between an acid & base. Eg:NaCl. When crysrallizedfrom aqueous solutions many salts crystallise as hydrates: CuSO4•5H2O -copper (II) sulfate PENTAhydrate CoCI2•6H2O - cobalt (II) chloride HEXAhydrate SnCl2•2H2O - stannous (tin II) chloride DIhydrate When heated, these salts lose their crystalline water & become “anhydrous salts”. HYDRATE is salt containing specific numbers of H2O molcules as part of solid crystalline structure. CuSO4•5H2O CuSO4 WATER OF HYDRATION is water retained as part of the solid crystalline structure of some salts. CoCI2 CoCI2•6H2O Salts of H2SO4 are sulphates. Salts of HCl are chlorides. Salts of HNO3 are nitrates.

25. strong or weak? HF Parent Acid: Parent Base: So…NaF is BASIC NaOH strong or weak? strong or weak? Parent Acid: Parent Base: So…Fe(NO3)3 is ACIDIC HNO3 Fe(OH)3 strong or weak? Parent Acid: Parent Base: So…NaCl is NEUTRAL strong or weak? HCl NaOH strong or weak?

26. Chemicals from common SALT Common Salt (NaCl) NaClis known as common salt. Important component of our food. Its main source is sea water. It also exists in the form of rocks and sodium chloride obtained from rocks is called rock salt. Used for preparing NaOH, baking soda, washing soda etc. Sodium Hydroxide or Caustic Soda (NaOH) NaOHis prepared by passing electricity through an aqueous solution of NaCl (also known as brine). 2NaCl (aq) + 2H2O (l) ------------2NaOH (aq) + Cl2 (g) + H2 (g) Process is known as chlor -alkali process due to the formation of Cl2 & NaOH (an alkali) as the products. Properties: 1.It is a white translucent solid. 2.It is readily soluble in water to give a strongly alkaline solution. 3.Crystals of NaOH are deliquescent(Hygroscopic- absorbs water)

27. Chemicals from common SALT Bleaching Powder (CaOCl2) (calcium oxychloride.) Prepared by passing chlorine gas through dry slaked lime. Ca (OH) 2 + Cl2 ----------- CaOCl2 + H2O Slaked lime Bleaching powder Uses- 1. For bleaching cotton and linen in textile industry. 2. For bleaching wood pulp in paper industry. 3. For disinfecting drinking water. Washing soda (Na2CO3 .10 H2O) (sodium carbonate decahydrate) Obtained by heating baking soda in turn is obtained by passing CO2 gas through sodium chloride solution saturated with ammonia . NaCl + H2O + CO2 + NH3 ----------------------- NH4Cl + NaHCO3 2 NaHCO3 ----------------------------- Na2 CO3 + H2O + CO2 Sodium hydrogen carbonate Sodium Carbonate Recrystallisation of sodium carbonates gives washing soda. Na2CO3+ 10 H2O -----------Na2 CO3 .10 H2O Uses- 1. It is used in glass, soap & paper industries. 2. It is used for removing permanent hardness of water. 3. It can be used as a cleaning agent for domestic purposes.

28. Chemicals from common SALT Baking soda (NaHCO3) Sodium hydrogen carbonate . Prepared by passing CO2 gas through brine solution saturated with NH3. NaCl+ H2O + CO2 + NH3 -------NH4Cl + NaHCO3 Ammonium chloride Sodium Hydrogen carbonate The precipitated sodium hydrogen carbonate is filtered off. Properties – 1. It is a white crystalline solid, sparingly soluble in water at room temperature. 2. Its aqueous solution is weakly alkaline due to hydrolysis. 3. On heating, it decomposes to give sodium carbonate and carbon dioxide. 2NaHCO3 Na2 CO3 + H2O + CO2 4. It reacts with acids to give CO2 gas. NaHCO3 + HClNaCl + H2O + CO2 Uses- 1. It is used as a component of baking powder.(baking soda & tartaric acid). 2. It is used in soda- acid fire extinguisher. 3. It acts as mild antiseptic and antacid.

29. Chemicals from common SALT Plaster of Paris (CaSO4 ..1/2 H2O) (POP) Its chemical name is calcium sulphate hemihydrate. It is obtained by heating Gypsum upto 373 K. CaSO4 .2H2O ---------------------- CaSO4 ..1/2 H2O + 11/2 H2O Gypsum Plaster of Paris On treatment with water it is again converted into gypsum and sets as a hard mass. CaSO4 ..1/2 H2O + 11/2 H2O ------------------- CaSO4 .2H2O Plaster of Paris Gypsum Uses – 1. It is used by Doctors for setting fractured bones. 2. It is used for making statues, models and other decorative materials

30. Measuring pH • Now that we know how to calculate pH of a solution, how do we measure it in the lab? There are several ways to test pH 1. By indicators (paper/chemicals) Blue litmus paper (red = acid) Red litmus paper (blue = basic) pH paper (multi-colored) Universal indicator (multi-colored) Indicators like phenolphthalein, Methyl Orange, Methyl Red. Natural indicators like red cabbage, radishes, Turmeric, Litmus, Logwood, Alizarin, China rose. 2. pH meter (7 is neutral, <7 acid, >7 base)

31. Choosing the Correct Indicator • Not all indicators shift colors at pH 7. • Many change colors over a wide range of pH values. • When testing a sample for acidity or basicity it is best to choose an indicator that has a color change close to pH 7 • Or use pH paper • Or use a pH meter to get a digital reading • Some indicators only work in a specific range of pH. Choosing the right one is important! • Once the drops are added, the sample is ruined.

32. INDICATORS What are indicators? Indicators are substances (DYES) that will change colors when they come in contact with acid or base. Why do we need indicators? Indicators are safe way to help scientist determine whether substance is an acid or alkali. Most are large molecules that act as weak acids. Color changes occur when the molecules is ionized (act as acid) or un-ionized (act as base). Universal indicator is an indicator which contains a mixture of substances that are able to give different colors corresponding to different pH values. Used to determine the strength of acids & alkalis by observing the change of its color. Color depends on the pH ie color changes with pH All indicator are weak base or weak acid the colour of indicator is due to ionic part of indicator. Table below shows colors of Universal Indicator corresponding to pH scale: Solutions must be colorless Eye must be able to detect the change Limitations of Indicators

33. Indicators Litmus Test Paper tests (litmus paper & pH paper) • Litmus is an indicator. It changes colour in acid and alkaline solutions. • Different indicator show different colour. • Litmus is red in acid. • Litmus is blue in alkali. Put a stirring rod into the solution and stir. Take the stirring rod out & place a drop of the solution from the end of the stirring rod onto a piece of the paper Read & record the color change. Note what the color indicates.

34. pH paper

35. Universal Indicator Universal indicator changes colour in acids & alkalis. ALKALIS ACIDS • Its colour shows the strength of an acid or alkali.

37. Methyl red goes from red at low pH to orange. Indicators An indicator changes color with changes in pH (numbers on tubes). Phenolphthalein goes from colorless to pink. Bromthymol blue from low pH to high pH.

38. Acidic—before neutralization Neutral— ”End Point” Basic— “overshot endpoint” • Acid-base titration is one commonly-used method of analysis. • When a titration is done, ACID is put into a flask using a pipet+ few drops of indicator, then base added from a buret until all acid reacted (equivalence point). • Point at which all acid reacted is shown by a color change (endpoint) in the indicator. • Volume OF BASE required in titration acid to be determined.

39. Hibiscus Result Methyl Orange & Phenolphthalein

40. Why other substance used can only detect the pH of alkali ? Equivalence point obtained  Coincident the one by standard indicator Flower extract  Use of mixed indicator • Why hibiscus can as the indicator for different pH ? Contains anthocyanine Pigment Pink, red, purple, violet and blue Dye extracted Changes its colour Hydrogen ion conc. of the solution 3.Any differences between the efficiency of hibiscus & phenolphthalein ?

41. pH METER • Tests the voltage of the electrolyte • Converts the voltage to pH • Very cheap, accurate • Must be calibrated with a buffer solution

42. Digestion and pH Digestive system • Digestion-process by which foods are broken down into simpler substances. • Mechanical digestion-physical process in which food is torn apart (mouth) • Chemical digestion- chemical reactions in which large molecules are broken down into smaller molecules. (stomach & small intestines) • Mouth-pH around 7. Saliva contains amylase, an enzyme which begins to break carbohydrates into sugars. • Stomach- pH around 2. Proteins are broken down into amino acids by the enzyme pepsin. • Small intestine-pH around 8. Most digestion ends. Small molecules move to bloodstream toward cells that use them mouth esophagus stomach large intestine small intestine

43. pH in Our Digestive System Our stomach produces hydrochloric acid. This dilute hydrochloric acid helps in digesting our food without harming the stomach. sometimes, excess of acid is produced due to various reasons. The excess acid in the stomach causes indigestion which produces pain and irritation. In order to cure indigestion and get rid of pain, we can take bases called ‘antacids’ (means ‘ant-acid’). Antacids are a group of mild bases which have no toxic effects on the body. Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This gives relief .

44. Thank you