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Acidic/Basic Characteristics

Acidic/Basic Characteristics. Determination of Acids and Bases. Most solutions of acids and bases are clear and colourless. To determine whether a solution is an acid or base an indicator is used. Chemical that changes colour as the concentration H + ( aq ) or OH - ( aq ) ions change

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Acidic/Basic Characteristics

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  1. Acidic/Basic Characteristics

  2. Determination of Acids and Bases • Most solutions of acids and bases are clear and colourless. • To determine whether a solution is an acid or base an indicator is used. • Chemical that changes colour as the concentration H+ (aq) or OH- (aq) ions change • Two common indicators are phenolphthalein and litmus. • Phenolphthalein clear in the presence of an acid turns dark pink in the presence of OH+ ions • Red litmus paper turns blue for bases • Blue litmus paper turns red for acids • Red Acid and Blue Basic

  3. pH Scale • Litmus cannot determine how strong the solution is. • The pH scale measures the acidity of the solution. In other words it can be used to determine the concentration of H+ ions present in the solution. • Scale is from 0 to 14 with 7 being a neutral solution • 0-7 acidic solution and 7-14 basic solution • Water contains H+ and OH- ions but only a few water molecules ionize • H2O(l) ↔ H+(aq) + OH-(aq) • Neutral water contains an equal number of ions. • pH of water is 7

  4. Reading The Scale

  5. Properties • Two factors determine how many H+ ions are in the solution. • Concentration: Amount of pure acid that is dissolved per one litre of water. • Ionization: The process of molecules becoming ions. • Percent Ionization is the number of molecules that will ionize for every 100 molecules that dissolve. • Complete Ionization – Strong Acids and Bases. • Partial Ionization – Weak Acids and Bases. • Strong acids and bases are very hazardous.

  6. Strong/Weak Acids

  7. Strong/Weak Bases

  8. Neutralization • Reaction between an acid and a base. • The resulting products are a salt and water. • Acid + Base  Salt + Water • A salt is an ionic compound • The combination of different acids and bases produces different salts. • Table salt, NaCl, can be produced from the following reaction. • HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)

  9. Swimming Pool • The process of neutralization is used to maintain pools. • Chlorine is used in pools to kill bacteria and algae. • Since chlorine gas is dangerous(corrosive and toxic), hypochlorous acid (HOCl) is used to keep pools clean. • To produce hypochlorous acid you must bubble chlorine gas through water. • A salt of HOCl can be produced by reacting with NaOH • Ideally pH should be between 7.2 and 7.8. If the water becomes too acidic (low pH) than a base (sodium carbonate) is used to neutralize the water. • If the pH becomes too high than hydrochloric acid can be used to remove the excess hydroxide ions.

  10. Acid Rain • When carbon dioxide go into the atmosphere it reacts with rainwater to produce carbonic acid. • CO2(g) + H2O(l)  H2CO3(aq) • This is how acid rain is produced • Can you think of a reaction we looked at before that involved carbonic acid. • Carbonated beverages contain carbonic acid. • So pop can’t be good for you right. • Uncontaminated rainwater has a pH of about 5.5 • Rainwater with a pH below 5.5 is considered to be acid rain

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