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Presentation On Acids And Bases

Published in: Chemistry | Science
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This PPT is suitable for the IGCSE and O Level Chemistry students. It only provides theoretical background of the topic. The worksheets and topical questions will be discussed during the tutoring sessions

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  1. Acids and Bases Chemistry (IGCSE / O-Level)
  2. What will you learn in this lesson? • About acids, bases and alkalis • Neutralization reaction • Acids and alkalis in terms of their effect on: (a) litmus (b) thymolphthalein (c) methyl orange • Characteristic properties of bases in terms of their reactions with: (a) acids (b) ammonium salts
  3. Acids
  4. Some Common Acids Y pe Organic acids Mineral acids Name ethanoic acid methanoic acid lactic acid citric acid carbonic acid hydrochloric acid nitric acid sulfuric acid phosphoric acid Formula CH3COOH HCOOH CÉHe07 H2C03 HCI HN03 H2S04 H3P04 weak weak weak weak weak strong strong strong strong Where found Or used In Vinegar in ant and nettle stings; used in kettle descaler in sour milk in lemons, oranges and other dtrus fruits in fizzy soft drinks used In cleaning metal surfaces; found as the dilute acid in the stomach used in making fertilisers and explosives in car batteries; used in making fertilisers, paints and detergents in anti-rust paint; used in making fertilisers
  5. Alkalis and Bases The oxides and hydroxides of metals that neutralize acid are called bases. A base neutralize an acid and in the result a salt is formed. This process is called neutralization. acid + base —4 salt + water Most bases are soluble in water and they are given a special name called alkali. Alkalis are generally used in laboratories as aqueous solutions. bases (e.g. CuQ MgO, CaO. NaOH, all neutralise acids alkalis are soluble bases (e.g. NaOH, KOH)
  6. Some Common Alkalis and Bases Alkalis feel soapy to the skin. They remove oils from your skin by converting them into soluble soaps, which can be washed away Name sofim hydroxide (caustic soda) potassium hydroxide (caustic potash) Strong Formula NäOH strong strong calcium hydroxide strong (limewater) NH or ammonia sol Lion weak (ammonium hydroxide) NH40H caldum oxide magnesium oxide moo Where found or used in oven deaners (deqreasinq agent); in making soap and paper; other industrial uses in making soft soaps and biodiesel to neutralise soil addity and acidic gases produced by power stations; has limited solubility in cleaning flu' ds in the home (degreaSng agent); in making fertilisers for neutralising soil acidity and industrial waste; in making cement and concrete in antacid indigestion tablets
  7. Alkali or Bases with Ammonium Salts In addition to their neutralization reaction with acids, bases will also react with ammonium salts to produce ammonia gas hydroxide sodium nitrate + ammonia NaOH(aq) H20(1) NHJ(g) ammonituu nitrate + oxide nitrate water + ammonia + caoc,) - + +
  8. Indicators Indicators are substances that changed their colors if they are put in acidic or alkaline solution. The commonly used indicators are litmus paper, thymolphthalein and methyl orange. Litmus paper soaked in litmus solution. It is found in two colors blue and red. Acid turns blue litmus paper to red and base turns red litmus paper to blue. Damped litmus paper is used to check gases acid / base The colour darqeof litmusin acid(red) and base (blue).
  9. Some Common Indicators icator thymolphthalein methyl orange Colour in acid coloudess red Neutral colour purple coloudess orange alkali blue blue yellow
  10. Universal Indicator A mixture of indicators that has different colors in solutions of different pH weakly.lkaline PHO 4 j orange yellow green blue vio'et
  11. The pH Scale A scaling running from below O to 14, used to expressing the acidity or alkalinity of a solution. A neutral solution has a pH of 7 • acids have a OH less than 7 • fie more acidic a solution, the lower the pH • neutral substances, such as pure water, have a pH of 7 alkalis have a PH greaterthan 7. in use in the taborato•rv.
  12. The pH Scale (contd.) highly acidic poorly acidic poorly alkaline highly alkaline hydrochloric acid (HCI) gastric juices lernon juice vin egar pure water, sugar solution baking soda solution household ammonia sodium hydroxide (NaOH)
  13. Practice Questions 1 2 3 a b c a b What do you understand by the word corrosive? Which acid is present in orange or lemon juice? What acid is present in vinegar? Methyl orange is an indicator. What does this mean? Is a solution acidic, alkaline or neutral if its pH is: i 11 iii 8 iv 37 Which solution is more Eidic: an acid with a pH of 4 or an acid with a pH of 1?
  14. Presence of H+ and OH - ions • Distilled water contains equal amount of H + and OH ions. It does not conduct electricity • Acid dissolved in water creates more 1-1+ ions in solutions and conduct electricity • Alkali solutions have more OH- ions than distilled water and conduct electricity • pH scale is made around the fact that acid solutions have this excess of hydrogen ions
  15. Presence of H+ and OH - ions (contd.) Litmus is affected by the presence of and OH- ions the hydrogen ions (H+) in add solutions tum litmus red • the hydroxide ions (OH—) in alkali sollions tum litmus blue. Purewater; —OH- Adid solution*" > OK pH tower litmus fha n blue solution:
  16. Presence of H+ and OH - ions (contd.) hydrochloric acid nitric •cid sulfuric •cid sodium hydroxide (caustic soda) ootassium hydroxide Ccaustic potash) kalis calcium hydroxide Climewater) ammonia solution (ammonium hydro*ide) H+(a andCE(aq) and N02'(aq) and Na and OH7(aq) and OH-(sa and OH and
  17. Neutralization Reaction A chemical reaction between an acid an a base to produce a salt and water only. It is summarized by the ionic equation: H+(aq) + OH-(aq) -s Hi0(1)
  18. Properties of Acids, Bases and Alkalis The properties of acids, bases and alkalis can be summarised as follows: • solutions contain an excess ofH+ ions and have a pH lower than 7.0 turn blue litmus red • are neutralisedby a base to give a salt and water only. • are the oxides and hydroxides of metåls • neutralise acids to give a salt and water only • are mainly insoluble in water. Alkalis: • are bases that dissolve in water, and feel soapy to the skin give solutions that contain an excess of OH— ions • give solutions with a pH greater than 7.0 and tum red litmus blue.
  19. Practice Questions 4 5 6 What Is the formula 6r: a b a b c sufiric acid hy&ochloric add? What statement can we make about the concentrations of hydrogen ions and hydrmddé Ions in water? Which ion is in excess in the solution of an alkali? Which ions are present i nitric acid solution li calcium hydr«lde sdueon iii ammonia solution? Which of the following compounds •re dlkalls? zinc oxide; magnestum oxide; potassium hydroxide; aluminlum hydroxide; ammonium hydroxide