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Acids and Bases 1

Acids and Bases 1. Boon Chemistry January 14 and 15, 2013. Catalyst. Use your flashcards to answer the following questions. When sodium hydroxide (a strong base) is dissolved in water, it conducts electricity. Sodium hydroxide is an example of an _______.

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Acids and Bases 1

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  1. Acids and Bases 1 Boon Chemistry January 14 and 15, 2013

  2. Catalyst • Use your flashcards to answer the following questions. • When sodium hydroxide (a strong base) is dissolved in water, it conducts electricity. Sodium hydroxide is an example of an _______. • According to the Bronsted-Lowry definition of acid and base, acids _____ a proton and bases _______ a proton. • What is pH? • Objectives • I can describe and compare the properties of strong acids, weak acids, strong bases and weak bases. • I can write acid/base chemical reaction equation and identify the conjugate acids and bases. • Agenda • Catalyst • Demonstration pH • Notes and white board practice: Properties of Acids and bases • Group work: conjugate acid and base pairs.

  3. Ouchi Chemistry Scores 4th out of 12 Alliance High Schoolson Benchmark 2! We are moving up!!! Think, Pair Share: Lets set a goal as a class for the next benchmark. What can we do to reach that goal?

  4. Demonstration: What is pH? • Introduction: • Read the introduction silently. Highlight the answers to following questions as you read: • What does pH measure? • The pH scale goes from _____ to _____. • A neutral solution has a pH of ______. An _____ has a pH below 7, and a _____ has a pH above 7. • Water has a pH of ______ and is therefore considered _____. • A solution with a pH of 2 has ten times more hydrogen ions in it than a solution with a pH of _______.

  5. Demonstration: What is pH? • Procedure: Watch as we measure the pH of several household acids and bases using an indicator. Based on the results, add the different household acids and bases to the pH scale below.

  6. Notes: Properties of acids and bases

  7. Notes: Properties of acids and bases

  8. Notes: Properties of acids and bases

  9. Acids and bases at the molecular level • Simulation! • As we go through the simulation fill in the questions and pictures on your worksheet.

  10. Icons for Acid Base Solutions

  11. Strong Acid Acidsare substances that readily donate a proton (a hydrogen ion H+) to another substance. Strong acids dissociate completely when dissolved in a solvent. In other words, every acid molecule donates a proton (H+). • Example: hydrochloric acid (stomach acid – pH = 2.0) HCl(g) + H2O(l) → H3O+(aq) + Cl-(aq)

  12. Weak Acid Draw a picture and graph depicting a weak acid solution. Weak acidsdo not dissociate completely when dissolved in a solvent. In other words, only some of the acid molecules donate a proton (H+) to the solvent. • Example: acetic acid (vinegar – pH = 3.0) • CH3COOH(aq) + H2O(l) ↔ H3O+(aq) + CH3COO-(aq)

  13. Strong Base Draw a picture and graph depicting a strong base solution. Basesare substances that accept a proton (a hydrogen ion H+) from another substance. Strong bases dissociate completely when dissolved in a solvent. In other words, every base molecule accepts a proton (H+). • Example: potassium hydroxide (caustic potash pH = 13) • KOH(aq) → K+(aq) + OH-(aq) • In the presence of an acid, the hydroxide ion (OH-) accepts a proton (H+) to form water.

  14. Weak Base Weak basesdo not dissociate completely when dissolved in a solvent. In other words, only some of the base molecules accept a proton (H+) from the solvent. • Example: ammonia (cleaning product pH=10) • NH3(aq) + H2O(l) ↔ NH4+(aq) + OH-(aq) Draw a picture and graph depicting a weak base solution.

  15. 1.Order the solutions from lowest to highest pH. A. X<Y<Z B. Y<X<Z C. Z<Y<X D. Z<X<Y E. Y<Z<X X Y Z

  16. 4. Which image is from a weak base? • X B. Y C. Z D. more than one E. none X Y Z

  17. 3. Which image is from a strong acid? A. X B. Y C. Z D. more than one E. none X Y Z

  18. 2.Order the solutions from lowest to highest pH. A. X<Y<Z B. Y<X<Z C. Z<Y<X D. Z<X<Y E. Y<Z<X X Y Z

  19. 5. Acids have pH from ___ to _____. Bases have a pH from ______ to _______.

  20. 6. What ALWAYS distinguishes a weak acid from a strong acid? • A weak acid doesn’t react much in water; strong acids completely react. • A weak acid is more dilute than a strong acid. • A weak acid has a higher pH than a strong acid. • Statements a and c are both characteristics that distinguish weak acids from strong acids. • Statements a, b, and c are all characteristics that distinguish weak acids from strong acids.

  21. 7. What ALWAYS distinguishes a weak base from a strong base? • A weak base doesn’t react much in water; strong bases completely react. • A weak base is more dilute than a strong base. • A weak base has higher pH than a strong base. • Statements a and c are both characteristics that distinguish weak bases from strong bases. • Statements a, b, and c are all characteristics that distinguish weak bases from strong bases.

  22. Bronsted-Lowry Acids and Bases • According to the Bronsted-Lowry theory, an acid is a proton (H+) donor, and a base is a proton acceptor. • Example: HCl + OH- Cl- + H2O The HCl acts as an acid, the OH- as a base.

  23. Bronsted-Lowry Quick Check • Thumbs up for true and thumbs down for false. • In the following equation, H2O acts as an acid by donating a proton. • PH3(aq) + H2O(l) ↔ PH4+(aq) + OH-(aq) On your white board, label the acid, base, conjugate acid, and conjugate base.

  24. Group Work • Work with the person next to you to complete the acid and base worksheet. • Label the acid, base, conjugate acid, and conjugate base for each equation. Draw arrows indicating how protons are donated.

  25. Exit Slip • Show your work on a half sheet of paper. Use your notes and include proper units. • How many liters is 770 mL? • A chemist dissolves 0.75 molNaCl in 500 mL of water. What is the molarity of the solution? • A solution contains 46 g of ethanol (C2H5OH) dissolved in 4 L of water. What is the molarity of the solution? • A 200 g water sample contains 0.5 mg chromium. What is the concentration of chromium in parts per million? • On a scale of 1-4 (with 4 the highest) rate your level of comfort with the new acids/bases material.

  26. Homework • Read pp. 530 – 538 pp. 538 # 1, 3, 5, 6, 7, 9, 13

  27. Exit Slip: Answers • How many liters is 770 mL? 770 mL = 0.770 L • A chemist dissolves 0.75 molNaCl in 500 mL of water. What is the molarity of the solution? 500 mL = 0.500 L 0.75 mol= x mol1.5 M 0.500 L 1 L • A solution contains 46 g of ethanol (C2H5OH) dissolved in 4 L of water. What is the molarity of the solution? convert from grams to moles. Molar mass of C2H5OH = 46 g/mol. 46 g ethanol = 1 mol ethanol 1 mol= x mol x = 0.25 M 4 L 1 L

  28. Exit Slip answers continued • A 200 g water sample contains 0.5 mg chromium. What is the concentration of chromium in parts per million? 0.5 mg = 0.0005 g 0.0005 g x 1,000,000 = 2.5 ppm 200 g 5. On a scale of 1-4 (with 4 the highest) rate your level of comfort with the new acids/bases material.

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