1 / 14

Unit Twelve Acids and Bases

Unit Twelve Acids and Bases. Strengths. What is an electrolyte? A solution that contains ions and will conduct electrical current Acids and bases ionize (molecular) or dissociate (ionic) into ions Dissociation – when ionic compounds break apart to form ions Examples: NaCl, NaOH, Na 2 SO 4

nash
Download Presentation

Unit Twelve Acids and Bases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Unit TwelveAcids and Bases

  2. Strengths • What is an electrolyte? • A solution that contains ions and will conduct electrical current • Acids and bases ionize (molecular) or dissociate (ionic) into ions • Dissociation – when ionic compounds break apart to form ions • Examples: NaCl, NaOH, Na2SO4 • Ionization – when molecular compounds break apart to form ions (acids) • Examples: HCl, H2SO4 • Dissolving – when solute molecules are surrounded by solvent molecules and go into solution

  3. Strengths • Strengths depend on how much ionization/dissociation takes place • Strong acids and bases completely ionize/dissociate in solution • 100% dissociated (lots of H+ and OH-) • Strong electrolytes • Weak acids and bases do not completely ionize/dissociate in solution • < 100% dissociated (only a few H+ and OH-) • Weak electrolytes

  4. Strong versus weak • For strong acids and bases we use a single arrow to indicate the forward reaction is favored • For weak acids and bases we use a double arrow to indicate the partial ionization (forward and reverse reactions take place)

  5. Strong Acids and Bases • There are six strong acids • HClO4 • H2SO4 • HNO3 • HCl • HBr • HI • There are eight strong bases • LiOH • NaOH • KOH • RbOH • CsOH • Ca(OH)2 • Sr(OH)2 • Ba(OH)2

  6. Water • Amphoteric – water can act as an acid or a base • Self-ionizations – water can also act as an acid and a base with itself! (Even neutral, pure, distilled water)

  7. Kw • In pure water at 25°C, the preceding reaction occurs only to a very small extent, resulting in equal, small concentrations of H+ and OH–. • [H+] = [OH–] = 1.0 x 10-7 M • Ion product constant for water (Kw) – the product of the concentration of H+ and OH–in aqueous solutions • Kw = [H+][OH–] • Kw = (1.0 x 10-7M)(1.0 x 10-7M) • Kw = 1.0 x 10-14 M • Can be used for aqueous solutions at 25°C (↑temp, ↑ movement, ↑ dissociation) • Kw will not change when the concentrations change because strengths are based on the amount of ionization.

  8. Kw • Since Kwis constant, and Kw = [H+] [OH‾], it follows that: • If [H+] increases, then [OH‾] decreases, and • If [H+] decreases, then [OH‾] increases. • In a neutral solution: [H+] = [OH-] • In an acidic solution: [H+] > [OH-] • In a basic solution: [H+] < [OH-]

  9. pH and pOH Scale • The pH scale relates to the strengths • pH scale measures the hydrogen ion concentration and the pOH measures the hydroxide ion concentration • Logarithmic scale – a change in 1 pH unit corresponds to a tenfold change in [H+] (lime (pH=2) versus plum(pH=3)) • pH < 7 : acidic solution • pH = 7 : neutral • pH > 7 : basic solution

  10. pOH 13 12 11 10 9 8 7 6 5 4 3 2 1

  11. Calculations • Kw = [H+] [OH‾] • pH = -log[H+] • pOH = -log[OH‾] • 14 = pH + pOH • [H+] = 10-pH • [OH‾] = 10-pOH

  12. Practice Problems • What are the [H+] and [OH‾] concentrations in a 0.01 M HCl solution? • What are the [H+] and [OH‾] concentrations in a 0.0001 M NaOH solution? • What are the [H+] and [OH‾] concentrations in a 0.00001 M HNO3 solution? • What is the pH of a 0.0001 M HNO3 solution? • What is the pOH of a 0.001 M KOH solution?

  13. Practice Problems • Calculate the [H+] of a solution with a pH of 8.37. • What is the concentration of OH- in a solution with a pOH of 4.80? • Calculate the pH of a solution with [OH-] = 1.3 x 10-2 M. Is the solution acidic or basic? Hint: Start with KW first to find [H+]. • Calculate the OH- concentration for a solution with a pH of 3.66.

  14. Worksheet Two will be due Thursday

More Related