Chapter 7 Acid & Bases part 1

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7.1; Introduction of Acid & Bases : SLISS 2012

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Chapter 7 Acid & Bases part 1

  1. 1. At the end of this lesson, students are able to: • State the meaning of acid, base and alkali. • State uses of acids, bases and alkalis in daily life. • Explain the role of water in the formation of hydrogen ions to show the properties of acids. • Explain the role of water in the formation of hydroxide ions to show the properties of alkalis. • Describe chemical properties of acids and alkalis.
  2. 2. Arrhenius’ definition: ACID BASE ALKALI Chemical Chemical Bases that can dissolve in water to compound that compound that produces ionises to produce can neutralise an hydroxide ion, OH- H+ or H3O+ in acid to form salt water. and water. H2O H2O Ex: HCl H+ + Cl- Base + acidsalt + Ex: NaOH (s) Na+ water + OH- Ex: MgO, ZnO, NaOH, KOH
  3. 3. The properties of acid is due to the presenceOf hydrogen ions, H+ (aq) H2O Acid H+Without water, acid will not behave as anacid.
  4. 4. The properties of alkali is due to the presenceOf hydroxide ions, OH- . H2O Alkali OH-Without water, alkali will not behave as analkali.
  5. 5. ACID ALKALI• Sour taste • Bitter taste• pH < 7 • pH > 7• Turn blue litmus • Turn red litmus paper to red paper to blue• React with bases to • React with bases to form salt & water form salt & water
  6. 6. Salt & Hydrogen gas Salt & water With With metal ACID baseEx: H2SO4 + Zn  Ex: HCl + NaOH ZnSO4 + H2  NaCl + H2O With metal carbonates Salt, carbon dioxide gas & water Ex: 2HCl + CaCO3  CaCl2 + CO2 + H2O
  7. 7. Metal hydroxide Salt & water With WithEx: Fe3+ + 3OH- metal ALKALI  Fe(OH)3 acid Ex: HCl + NaOH ion (precipitate)  NaCl + H2O Heat with ammonium salt Ammonia gas, water and salt Ex: NH4+ + OH-  NH3 + H2O
  8. 8. H2SO4 Uses Of Carbonic Acid AcidBenzoic acid, ethanoic acid Nitric Acid, HCl
  9. 9. To clean metals beforeelectroplating.To makepaints, detergents, fertilizers,electrolyte.To coagulate latex.
  10. 10. To preserve foodA component of vinegarTo make carbonated acid
  11. 11. MgOH: neutralises acids Uses Of Al(OH)3, Mg(OH)2 : alkali Alkali neutralise excess acid in our stomach NaOH NH3 solution
  12. 12. To make Fertilizers, to keeplatex in liquid form, as a sinkcleaning agent.To make soap, detergents.To make toothpaste, gastricpills (antacids).
  13. 13. 7.1 : ASIDS AND BASES The following is some information on magnesium hydroxide: Magnesium hydroxide is one of the ingredients found in toothpaste and potassium hydroxide is used as the electroyte in alkaline batteries. Magnesium hydroxide is a base and potassium hydroxide is an alkaline.a) What is base?b) How is alkali different from a base?c) State three physical properties of an alkali.d) Write a balanced chemical equation to show the reaction between hydrochloric acid and magnesium hydroxide.
  14. 14. What is base? A base is a substance that react with an acid to form salt and water only.How is alkali different from a base? An alkali is a soluble base that forms a solution when dissolved in water and ionises to produce hydroxide ions.State three physical properties of an alkali. Alkali is bitter. Slippery. Turn red litmus paper blue.Write a balanced chemical equation to show the reaction between hydrochloric acid and magnesium hydroxide. Mg(OH)2 (s) + 2HCl (aq)  MgCl2 (aq) + 2H2O (l)

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