Acid And Base

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Definitions and strength of acid and alkali

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Acid And Base

  1. 1. ACID AND BASE Meaning: An acid is a chemical substance which ionises in water to produce hydrogen ions, H + or hydroxonium ion, H 3 O + . A base is a chemical substance which reacts with acid to produce salt and water A alkali is a chemical substance which ionizes in water to produce hydroxide ions, OH - Faridah Hamat SASER 2008
  2. 2. Strong Acid, Weak Acid <ul><li>Strong acid: Acid which ionizes completely when dissolve in water to produce high concentration of hydrogen ion, H + </li></ul><ul><li>Example: HCl, HNO 3 , H 2 SO 4 </li></ul><ul><li>HCl  H + + Cl - </li></ul><ul><li>H + + H 2 O  H 3 O + </li></ul><ul><li>(Hydroxonium ion) </li></ul>Faridah Hamat SASER 2008
  3. 3. Cont…. <ul><li>Weak acid: Acid which ionises partially when dissolve in water to produce low concentration of hydrogen ion, H + </li></ul><ul><li>Example: Ethanoic acid </li></ul><ul><li>CH 3 COOH  CH 3 COO - + H + </li></ul>Faridah Hamat SASER 2008
  4. 4. Strong Alkali, Weak Alkali <ul><li>Strong alkali: Alkali which ionizes completely when dissolve in water to produce high concentration of hydroxide ion, OH - </li></ul><ul><li>Example: NaOH, KOH </li></ul><ul><li>Weak alkali: Alkali which ionises partially when dissolve in water to produce low concentration of hydroxide ion, OH - </li></ul><ul><li>Example: NH 3(aq) </li></ul>Faridah Hamat SASER 2008
  5. 5. Basicity of Acid <ul><li>Basicity of an acid is the maximum number of hydrogen ions that is produced when one molecule of an acid ionizes in water </li></ul><ul><li>Monoprotic acid: Hydrochloric acid, HCl and nitric acid, HNO 3 . </li></ul><ul><li>e.g : H Cl  H + + Cl - </li></ul><ul><li>Diprotic acid : Sulphuric acid, H 2 SO 4 </li></ul><ul><li>e.g: H 2 SO 4  2H + + SO 4 2- </li></ul>Faridah Hamat SASER 2008
  6. 6. Cont…… <ul><li>Triprotic acid: Phosphoric acid, H 3 PO 4 </li></ul><ul><li>e.g: H 3 PO 4  3H + + PO 4 3- </li></ul>Faridah Hamat SASER 2008
  7. 7. Physical Properties of Acid <ul><li>Acids have a sour taste </li></ul><ul><li>Solution of acids has pH less than 7 </li></ul><ul><li>Solution of acid change blue litmus paper to red. </li></ul><ul><li>Aqueous solution of acids are electrolytes because the presence of freely moving ions (H + ) </li></ul>Faridah Hamat SASER 2008
  8. 8. Chemical Properties of Acid <ul><li>Acid + metal  salt + hydrogen gas </li></ul><ul><li>2HCl (aq) + Mg (s)  MgCl 2 (aq) + H 2 (g) </li></ul><ul><li>Acid + base  salt + water </li></ul><ul><li>H 2 SO 4 (aq) + CuO (s)  CuSO 4 (aq) + H 2 O(l) </li></ul><ul><li>Acid + alkali  salt + water </li></ul><ul><li>HNO 3 + NaOH (aq)  NaNO 3 + H 2 O </li></ul>Faridah Hamat SASER 2008
  9. 9. Cont….. <ul><li>Acid + carbonate metal  salt + water + carbon dioxide </li></ul><ul><li>2HCl + CaCO 3  CaCl 2 + H 2 O + CO 2 </li></ul>Faridah Hamat SASER 2008
  10. 10. <ul><li>An acid shows its acidic properties only when it is dissolved in water. This is because without water, an acid still exits as molecules and there are no hydrogen ions, H + present. </li></ul><ul><li>In the dry acid, the ions in the acid are fixed in the lattice positions. </li></ul>Faridah Hamat SASER 2008
  11. 11. Physical Properties of Alkali <ul><li>a bitter taste </li></ul><ul><li>pH greater then 7 </li></ul><ul><li>change red litmus paper to blue </li></ul><ul><li>Aqueous solution of alkalis are electrolytes because the presence of freely moving ions. </li></ul>Faridah Hamat SASER 2008
  12. 12. Chemical Properties of Alkali <ul><li>Acid + alkali  salt + water </li></ul><ul><li>HNO3 + NaOH  NaNO 3 + H 2 O </li></ul><ul><li>Alkali + metal ion  insoluble metal hydroxide </li></ul><ul><li>2OH - + Mg 2+  Mg(OH) 2 </li></ul><ul><li>Alkali + ammonium salt </li></ul><ul><li> salt + water + ammonia </li></ul><ul><li>NaOH + NH 4 Cl  NaCl + H 2 O + NH 3 </li></ul>Faridah Hamat SASER 2008
  13. 13. USES Faridah Hamat SASER 2008 Uses of acids Uses of bases and alkalis * Make industrial products such as paints, detergents, fertilizers. * Food preservative such as vinegar, citric acid and ascorbic acid. * Electrolyte in lead-acid accumulator. * Use as laboratory reagents * Make soaps, shampoos and detergents. * Make several of medicines, such as antacid and aspirin. * Use as laboratory reagents
  14. 14. Molarity (mol dm -3 ) = Number of Mole Volume, dm 3 Example: Calculate the molarity of 0.4 moles sulphuric acid in 250cm 3 solution. Solution : Number of mole = MV 1000 Molarity = number of mole x 1000 = 0.4 x 1000 250 250 = 1.6 mol dm -3 CONCENTRATION Faridah Hamat SASER 2008
  15. 15. <ul><li>PREPARED BY: </li></ul><ul><li>PN. FARIDAH BINTI HAMAT </li></ul><ul><li>SASER </li></ul>Faridah Hamat SASER 2008

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