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What are they? There are different definitions for acids and bases dependent on the circumstances.

ACIDS AND BASES. What are they? There are different definitions for acids and bases dependent on the circumstances. Operational Definition - (Properties in which they differ). Acids 1. react with carbonates to produce carbon dioxide gas. 2. change pink phenolphthalein to colourless

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What are they? There are different definitions for acids and bases dependent on the circumstances.

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  1. ACIDS AND BASES What are they? There are different definitions for acids and bases dependent on the circumstances. Operational Definition - (Properties in which they differ)

  2. Acids 1. react with carbonates to produce carbon dioxide gas. 2. change pink phenolphthalein to colourless 3. make litmus paper red 4. make bromothymol blue turn yellow 5. taste sour 6. have a pH below 7 7. react with most metals and produce hydrogen gas

  3. Bases 1. don’t react with carbonates to produce carbon dioxide gas. 2. change colourless phenolphthalein to pink 3. make red litmus paper turn blue 4. make bromthymol blue turn blue 5. taste bitter 6. have a pH above 7

  4. NaCO3 Acid Acids 1. ____________ react with carbonates to produce carbon dioxide gas. CO2 bubbles

  5. 2. ___________ change colourless phenolphthalein to pink Base Phenolphthalein

  6. Acids 3. _________ make blue litmus paper turn red Phenolphthalein Litmus paper

  7. Acids 4. __________make bromthymol blue turn yellow Acid or base? Bromthymol blue

  8. A lemon tastes sour. Is it an acid or a base? Acid

  9. Is this solution an acid or a base? 7.0 1.8 Acid pH meter

  10. Acid Zn Is this solution an acid or a base? H2

  11. Conceptual Definitions of Acids and Bases A chemist named Arrhenius recognized acids were molecular compounds and as such didn't conduct electricity as liquids since they didn't release ions. But he observed that when acids were combined with water they did conduct electricity. He also observed bases conducted electricity as liquids and when they were combined with water. Bases were ionic but acids weren't.

  12. Arrhenius’s Definition of Acids and Bases Acids are substances which react in water and produce hydronium ions. HCl(g) + H20 -------> H301+(aq) + Cl1-(aq) Bases are substances which react with water and produce hydroxide ions. NH3(g) + H20 ------> NH41+(aq)+ OH1-(aq)

  13. Homework from Nelson Pg. 367 #1-7,

  14. This concept has its limitations however. Can’t substances be classified as acids or bases without the involvement of water?

  15. Bronstead's and Lowry's Definition of Acids and Bases Acids are substances which donateprotons and bases are substances which acceptprotons. In the examples above HCl(g) is an acid because it donates protons to H2O molecules and NH3 is a base because it accepts protons from H2O molecules.

  16. conjugate pair conjugate pair Conjugate Acid - Base Pairs - When using the Bronsted concept for acids and bases it is convenient to consider all acid - base reactions as reversible equilibria. For instance when sulfurous acid, H2SO3 reacts with water the following equilibrium is established: acid base acid base H2SO3 + H2O H301+ + HSO31-

  17. conjugate pair conjugate pair H2SO3 + H2OH301+ + HSO31- acid baseacid base In the forward direction the H2SO3 is the proton donor so it’s the acid and the H2O is the proton acceptor so it’s the base. In the reverse direction the H301+ is the proton donor so it’s the acid and the HSO31- is the proton acceptor so it’s a base.

  18. conjugate pair conjugate pair H2SO3 + H2O H301+ + HSO31- acid base acid base When looking at both forward and reverse reactions it is easy to pick out a pair of molecules which differ by a single proton (H atom without its electron). These pairs are called conjugate acid-base pairs.

  19. Homework from Nelson Pg. 389 # 17-20 Pg. 392 # 8-11

  20. Why do acids of equal concentration have different levels of conductivity? Some acids are stronger than others. Why? Let's look at a container of water.

  21. Water molecules

  22. HCl molecules

  23. Cl1- Strong acids and bases Totally ionize

  24. Water molecules

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