Acids & Bases

1. Acids&Bases They are everywhere.. In your food In your house EVEN IN YOU!!!!! Dr Seemal Jelani

2. What is an acid? • An acid is a solution that has an excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour". • The more H + ions, the more acidic the solution. Dr Seemal Jelani

3. Properties of an Acid • Tastes Sour • Conduct Electricity • Corrosive, which means they break down certain substances • Many acids can corrode fabric, skin, and paper Dr Seemal Jelani

4. Introduction to Acids (con’t) • Lactic acid is also produced by bacteria in milk – this is why milk turns sour. • Acids occur naturally in many fruits. • Insects such as millipedes, scorpions, and ants use acids to deter predators. • A physician may use a solution of boric acid to rinse out your eyes, but a drop or two of many other acids would blind you. • Some acids add a tangy, sour flavour to foods and drinks, while others are deadly.

5. Some acids react strongly with metals • Turns blue litmus paper red Dr Seemal Jelani

6. Definitions Arrehenius only in water • Acids – produce H+ • Bases - produce OH- • Acids – donate H+ • Bases – accept H+ • Acids – accept e- pair • Bases – donate e- pair Bronsted-Lowry any solvent Lewis used in organic chemistry, wider range of substances Dr Seemal Jelani

7. The hydrogen ion in aqueous solution Examples H+ + H2O  H3O+ (hydronium ion) Arrhenius HCl NaOH Bronsted-Lowry HCl HCN NH3 :NH3 Lewis BF3 Dr Seemal Jelani

8. Word Connect • The word “acid” comes from the Latin acidus, meaning “sour” • Think of the taste of fruits such as lemons or limes • These fruits contain citric acid • Vinegar, a common household product, contains acetic acid.

9. Chemists sometimes use the term “alkali” for a base that is soluble in water • This word shows the Arabic origin of chemistry • The earliest source of bases was the ash obtained by burning plants • Thus the Arabic word alkali means “ashes of a plant.” Dr Seemal Jelani

10. Alkali salts are soluble hydroxides of alkali metals and alkaline earth metals, of which common examples are: • Sodium hydroxide – often called "caustic soda" • Potassium hydroxide – commonly called "caustic potash" • Lye – generic term for either of the previous two or even for a mixture • Salts of alkali • Reaction with water • What is an example of a strong alkali?(pH 14) Dr Seemal Jelani

11. Strong acids and weak acids • High concentration of Hydrogen ions • Low concentration of Hydrogen ions • What is difference between base and alkali? • Bases are substances that react with acids and neutralize them. • They are usually metal oxides, metal hydroxides, metal carbonates or metal hydrogen carbonates. Many bases are insoluble - they do not dissolve in water. If a base does dissolve in water, we call it an alkali. Dr Seemal Jelani

12. What is an alkaline? • The “alkaline” in alkaline water refers to its pH level. The pH level is a number that measures how acidic or alkaline a substance is on a scale of 0 to 14 • Examples: acids, base, alkaline(pH > 7.0) Dr Seemal Jelani

13. An alkaline solution is a mixture of base solids dissolved in water. • The potential of hydrogen, also known as the pH scale, measures the alkalinity or acidity level of a solution. • The scale ranges from zero to 14. The midpoint 7 represents a neutral pH. • A neutral solution is neither an acid nor alkaline. pH levels below 7 indicate an acidic solution, and numbers above 7 indicate an alkaline solution. • The pH is a measurement of intensity, not capacity Dr Seemal Jelani

14. Is alkaline a base or acid? • The solution is neither acidic or basic. ... Because the base "soaks up" hydrogen ions, the result is a solution with more hydroxide ions than hydrogen ions. • This kind of solution is alkaline. • Acidity and alkalinity are measured with a logarithmic scale called pH. Dr Seemal Jelani

15. pH • pH is the measure of acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline. • The pH is equal to −log10c, where c is the hydrogen ion concentration in moles per litre. • The pH in the chemistry test used to test the acidity of substances stands for 'potential hydrogen,' Dr Seemal Jelani

16. What are pH levels? • why is it important? • The importance of pH. The pH level of water measures how acidic it is (pH stands for potential hydrogen, referring to how much hydrogen is mixed with the water.) 7 is a balanced pH for water. Anything below 7 indicates the water is acidic, and if it's above 7 it is alkaline. Dr Seemal Jelani

17. What should your body pH be? • Those levels vary throughout your body.  • Your blood is slightly alkaline, with a pH between 7.35 and 7.45.  • Your stomach is very acidic, with a pH of 3.5 or below, so it can break down food. Dr Seemal Jelani

18. Why is pH so important to life? • Acids and bases are important in living things because most enzymes can do their job only at a certain level of acidity. • Cells secrete acids and bases to maintain the proper pH for enzymes to work. ... • The acidic environment helps with the digestion of food Dr Seemal Jelani

19. What does a pH of 5.5 in urine mean? • A neutral pH is 7.0. The higher the number, the more basic (alkaline) it is. • The lower the number, the more acidic your urine is. • The average urine sample tests at about 6.0. If your urine sample is lower, this could indicate an environment conducive to kidney stones. Dr Seemal Jelani

20. Uses of Acids • Acetic Acid = Vinegar • Citric Acid = lemons, limes, & oranges. It is in many sour candies such as lemonhead & sour patch. Dr Seemal Jelani

21. Ascorbic acid = Vitamin C which your body needs to function. • Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics. • Car batteries Dr Seemal Jelani

22. What is a base? • A base is a solution that has an excess of OH- ions. • Another word for base is alkali. • Bases are substances that can accept hydrogen ions Dr Seemal Jelani

23. Bases are bitter-tasting compounds with a slippery feel. Most soaps and drainers and window cleaners are bases.

24. Properties of a Base • Feel Slippery • Taste Bitter • Corrosive • Can conduct electricity. (Think alkaline batteries.) • Do not react with metals. • Turns red litmus paper blue. Dr Seemal Jelani

25. Uses of Bases • Bases give soaps, ammonia, and many other cleaning products some of their useful properties. Dr Seemal Jelani

26. The OH- ions interact strongly with certain substances, such as dirt and grease. • Chalk and oven cleaner are examples of familiar products that contain bases. • Your blood is a basic solution. Dr Seemal Jelani

27. Defining Indicators • Two of the most common indicators are phenolphthalein and litmus. • Litmus is a compound that is extracted from lichens, a plant-like member of the fungi kingdom • Litmus paper is made by dipping paper in litmus solution.

28. Chemical indicator, any substance that gives a visible sign, usually by a colour change. • What are indicators give examples? • Acid-Base Indicator Examples. • The best known pH indicator is litmus. Thymol Blue, Phenol Red and Methyl Orange are all common acid-base indicators. • Red cabbage can also be used as an acid-base indicator

29. What are natural indicators give examples? • An acid (e.g. vinegar, lemon juice), purple in an alkali (e.g. bicarbonate of soda, bleach) and green in something that is neutral (e.g. water). • Many plants contain their own indicators – turmeric, red cabbage juice and beetroot juice are three good examples. Other examples are tea and red grape juice. Dr Seemal Jelani

30. How do indicators work in chemistry? • pH indicators detect the presence of H+ and OH-. • They do this by reacting with H+ and OH-: they are themselves weak acids and bases. • If an indicator is a weak acid and is coloured and its conjugate base has a different colour, deprotonation causes a colour change. Dr Seemal Jelani

31. What are some examples of indicators? Some Common Indicators Dr Seemal Jelani

32. pH Scale • pHis a measure of how acidic or basic a solution is. • The pH scale ranges from 0 to 14. • Acidic solutions have pH values below 7 • A solution with a pH of 0 is very acidic. • A solution with a pH of 7 is neutral. • Pure water has a pH of 7. • Basic solutions have pH values above 7. Dr Seemal Jelani

33. Acid – Base Reactions • A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions. Dr Seemal Jelani

34. Acid – Base reactions • Each salt listed in this table can be formed by the reaction between an acid and a base. Dr Seemal Jelani

35. Neutralization In general: Acid + Base  Salt + Water All neutralization reactions are double displacement reactions. HCl + NaOH  NaCl + HOH HCl + Mg(OH)2 H2SO4 + NaHCO3 Dr Seemal Jelani

36. Strong and Weak Acids/Bases Strong acids/bases – 100% dissociation into ions HCl NaOH HNO3 KOH H2SO4 Weak acids/bases – partial dissociation, both ions and molecules CH3COOH NH3 Dr Seemal Jelani

37. - H+ + H+ When life goes either way amphoteric (amphiprotic) substances Acting like a base Acting like an acid HCO3- H2CO3 CO3-2 accepts H+ donates H+ Dr Seemal Jelani