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Acids and Bases

Acids and Bases. Unit 8- Biochemistry Assignment # 1. Acids and Bases. The concepts acids and bases were loosely defined as substances that change some properties of water. One of the criteria that was often used was taste. Substances were classified salty-tasting sour-tasting

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Acids and Bases

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  1. Acids and Bases Unit 8- Biochemistry Assignment # 1

  2. Acids and Bases • The concepts acids and bases were loosely defined as substances that change some properties of water. • One of the criteria that was often used was taste. • Substances were classified • salty-tasting • sour-tasting • sweet-tasting • bitter-tasting • Sour-tasting substances would give rise to the word 'acid', which is derived from the Greek word oxein, which mutated into the Latin verb acere, which means 'to make sour' • Vinegar is a solution of acetic acid. Citrus fruits contain citric acid.

  3. Acids • React with certain metals to produce hydrogen gas. • React with carbonates and bicarbonates to produce carbon dioxide gas Bases • Have a bitter taste • Feel slippery. • Many soaps contain bases.

  4. Properties of Acids • Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) • Taste sour • Corrode metals • Good Electrolytes • React with bases to form a salt and water • pH is less than 7 • Turns blue litmus paper to red “Blue to Red A-CID”

  5. Properties of Bases • Generally produce OH- ions in water • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water • pH greater than 7 • Turns red litmus paper to blue “BasicBlue”

  6. Bronsted-Lowry Definition Acid - neutral molecule, anion, or cation that donates a proton. Base - neutral molecule, anion, or cation that accepts a proton. Example HCl + H2O  H3O+ + Cl-

  7. pH and acidity The pH values of several common substances are shown at the right. Many common foods are weak acids Some medicines and many household cleaners are bases.

  8. Neutralization An acid will neutralize a base, giving a salt and water as products Examples Acid Base Salt water HCl + NaOH  NaCl + H2O H3PO4 + 3 KOH  K3PO4 + 3 H2O A salt is an ionic compound that is formed from thepositive ion (cation)of thebaseand thenegative ion (anion) of the acid

  9. Common Strong Acids/Bases Strong Acids Hydrochloric Acid Nitric Acid Sulfuric Acid Perchloric Acid Strong Bases Sodium Hydroxide Potassium Hydroxide Barium Hydroxide Calcium Hydroxide

  10. Salts • A salt is an ionic compound that is formed from thepositive ion (cation)of thebaseand thenegative ion (anion) of the acid Example HBr + NaOH  NaBr + H2O anioncationSalt

  11. Salts • If a salt is the result of a -- Strong acid and a strong base, the pH is near neutral. HCl + NaOH  NaCl + H2O. -- Weak acid and a strong base, the pH will be greater than 7. CH3COOH + NaOH  NaCH3COO + H2O -- Strong acid and a weak base, the pH will be lower than 7. NH4OH + HCl  NH4Cl +H2O -- Weak acid and a weak base, the pH depends on whether the acid or the base is stronger.

  12. Homework- Assignment #3(Due Friday!) • An "evil" genius is plotting to take over the world by manipulating acids and bases. The forces of "good” uncover the plot and set in motion plans to neutralize the threatening acids and bases. Write a humorous film script or story that dramatizes the outrageous characters and describe the adventure. • 5 paragraphs is fine, unless you want it to be longer! 

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