Acid base notes

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Acid base notes

  1. 1. Chemistry Unit 7 Acids and Bases
  2. 2. Acids <ul><li>An acid is a substance that ionizes in water to produce hydrogen ions (H + ) </li></ul><ul><li>The strength of an acid depends on how completely the substance ionizes. Strong acids completely ionize in water. Weak acids ionize only slightly. </li></ul>
  3. 3. Base <ul><li>A base is a substance that ionizes in water to produce hydroxide ions (OH - ) </li></ul><ul><li>The strength of a base depends on how completely the substance ionizes into metal ions and hydroxide ions in water. Strong bases ionize completely. Weak bases do not. </li></ul>
  4. 4. Basic Acidic Neutral H+ H+ H+ OH- OH- OH- Solution Solution Solution Which solution is Acidic? Basic? Neutral???
  5. 5. Acids and Bases <ul><li>Produce H+ ions in water </li></ul><ul><li>Have a sour taste </li></ul><ul><li>Break down metals </li></ul><ul><li>Formula starts with H </li></ul><ul><li>Poisonous and corrosive to skin </li></ul><ul><li>pH less than 7 </li></ul><ul><li>Produce OH- ions in water </li></ul><ul><li>Have a bitter taste and a slippery feel </li></ul><ul><li>Break down fats and oils </li></ul><ul><li>Formula ends with OH </li></ul><ul><li>Poisonous and corrosive to skin </li></ul><ul><li>pH greater than 7 </li></ul>
  6. 6. Acids and Bases <ul><li>ACIDS </li></ul><ul><li>Examples: vinegar, lemon juice, aspirin, stomach acid, battery acid, cola, milk </li></ul><ul><li>BASES </li></ul><ul><li>Examples: soap, shampoo, ammonia, drain cleaner, antacids </li></ul>
  7. 7. Neutral Substances <ul><li>pH = 7 </li></ul><ul><li>Safe to ingest and leave on skin </li></ul><ul><li>Concentrations of H + ions and OH - ions are equal </li></ul><ul><li>Examples: dH2O, salts, most cosmetics, lotions, eye drops, etc. </li></ul>
  8. 8. Neutralization Reactions <ul><li>When an acid is added to a base, the end products are always salt and water. (neutral) </li></ul><ul><li>A salt is defined as the neutral end product of an acid/base reaction. </li></ul><ul><li>ACID + BASE  SALT + WATER </li></ul><ul><li>H 2 S + Ca(OH) 2  CaS + H 2 O </li></ul><ul><li>What is wrong with this equation??? </li></ul>
  9. 9. Balance the final equation! <ul><li>H 2 S + Ca(OH) 2  CaS + H 2 O </li></ul><ul><li>1 Ca 1 </li></ul><ul><li>1 S 1 </li></ul><ul><li>4 H 2 </li></ul><ul><li>2 O 1 </li></ul><ul><li>H 2 S + Ca(OH) 2  CaS + 2 H 2 O </li></ul>
  10. 10. Neutralization Reactions <ul><li>Try another example: </li></ul><ul><li>Acid + Base  Salt + Water </li></ul><ul><li>H 2 SO 4 + NaOH  Na 2 SO 4 + H 2 O </li></ul><ul><li>1 Na 2 </li></ul><ul><li>1 SO 4 1 </li></ul><ul><li>3 H 2 </li></ul><ul><li>1 O 1 </li></ul><ul><li>H 2 SO 4 + 2 NaOH  Na 2 SO 4 + 2 H 2 O </li></ul>
  11. 11. Take it one step further… <ul><li>Sulfurous acid and sodium hydroxide yields sodium sulfite and water. </li></ul><ul><li>H 2 SO 3 + NaOH  Na 2 SO 3 + H 2 O </li></ul><ul><li>1 Na 2 </li></ul><ul><li>1 SO 3 1 </li></ul><ul><li>3 H 2 </li></ul><ul><li>1 O 1 </li></ul><ul><li>H 2 SO 3 + 2NaOH  Na 2 SO 3 + 2H 2 O </li></ul>
  12. 12. One Last Step <ul><li>Hydrochloric acid and sodium hydroxide yields what??? </li></ul><ul><li> HCl + NaOH  </li></ul><ul><li>One product will always be water. </li></ul><ul><li>HCl + NaOH  H 2 O + </li></ul><ul><li>The other product will be the + ion of the base bonded with the – ion of the acid. </li></ul><ul><li>HCl + NaOH  H 2 O + NaCl </li></ul>
  13. 13. pH Scale <ul><li>pH – a number used to denote the hydrogen ion concentration, or acididty, of a solution </li></ul><ul><li>pH Scale Typically runs from 0 – 14 </li></ul><ul><li>0 7 14 </li></ul>Acidic Basic Neutral
  14. 14. pH Indicators <ul><li>A chemical substance that changes color in the presence of an acid and/or a base. </li></ul><ul><li>pH paper – Dip the paper, match color to scale on vial to determine numeric pH. </li></ul><ul><li>pH<7 = acid, pH>7 = base, pH = 7 neutral </li></ul><ul><li>2) Litmus – Dip one red and one blue paper. </li></ul><ul><li>Red stays red, blue turns red  Acid </li></ul><ul><li>Blue stays blue, red turns blue  Base </li></ul><ul><li>Red stays red, blue stays blue  Neutral </li></ul>
  15. 15. pH Indicators <ul><li>Bromthymol Blue – Add a few drops of bromthymol blue to the substance. </li></ul><ul><li>If the blue color turns to yellow  Acid </li></ul><ul><li>If the blue color stays blue  Base </li></ul><ul><li>Phenolphthalein – Add a few drops of phenolphthalein to the substance. </li></ul><ul><li>If the clear liquid turns to pink  Base </li></ul><ul><li>If the clear liquid remains clear  Acid </li></ul>

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