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Strong Electrolytes

Strong Electrolytes. Strong acids Strong bases Soluble ionic salts. Precipitation Reactions. Example. Reaction of AgNO 3 (aq) with NaCl (aq). Ag NO 3 ( aq ) + K Cl ( aq )  AgCl ( s ) + KNO 3 ( aq ). Insoluble ionic compound (AgCl). Gravimetric Analysis.

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Strong Electrolytes

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  1. Strong Electrolytes • Strong acids • Strong bases • Soluble ionic salts

  2. Precipitation Reactions Example Reaction of AgNO3(aq)with NaCl (aq) AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq) Insoluble ionic compound (AgCl)

  3. Gravimetric Analysis Includes all analytical methods in which the final stage involve weighing Gravitational methods that employ precipitation reactions are commonly used in laboratories Precipitation followed by isolation and weighing the dry precipitate

  4. An Example (Gravimetric Analysis) • Consider the problem of determining the amount of lead in a sample of drinking water. • Adding sodium sulfate (Na2SO4) to the sample will precipitate lead(II) sulfate. • The PbSO4 can then be filtered, dried, and weighed.

  5. Soluble and insoluble ionic compounds Solubility guidelines for common ionic compounds in water

  6. Metathesis comes from a Greek word that means “to transpose” AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq) Insoluble ionic compound Metathesis (Exchange) Reactions

  7. The molecular equation lists the reactants and products in their molecular form. AgNO3 (aq) + KCl(aq) AgCl(s) + KNO3 (aq) Molecular Equation

  8. cross out anything that does not change from the left side of the equation to the right in the complete ionic equation. Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl(s) + K+(aq) + NO3-(aq) Ag+(aq) + Cl-(aq) AgCl(s) Net Ionic Equation Net Ionic Equation Complete Ionic Equation Write all soluble ions that exist in reactant and products

  9. Those things that didn’t change (and were deleted from the net ionic equation) are called spectator ions. Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl(s) + K+(aq) + NO3-(aq) Spectator Ions

  10. Writing Net Ionic Equations • Write a balanced molecular equation. • Dissociate all strong electrolytes. • Cross out anything that remains unchanged from the left side to the right side of the equation. • Write the net ionic equation with the species that remain.

  11. Monoprotic Acid H2SO4 (aq) H+ (aq) + HSO4- (aq) Diprotic Acid HSO4- (aq) H+ (aq) + SO42- (aq) Acids • Substances that increase the concentration of H+ when dissolved in water (Arrhenius). • Proton donors (Brønsted–Lowry).

  12. Strong Acids There are only seven strong acids: • Hydrochloric (HCl) • Hydrobromic (HBr) • Hydroiodic (HI) • Nitric (HNO3) • Sulfuric (H2SO4) • Chloric (HClO3) • Perchloric (HClO4)

  13. Weak Acids • Hydrofluoric Acid (monoprotic) • Acetic Acid (monoprotic) • Phosphoric Acid (triprotic) Notice that acetic acid is extremely soluble in water but it is a weak acid and a weak electrolyte

  14. Bases do not have to be hydroxides (e.g NH3) Bases • Substances that produce OH− when dissolved in water (Arrhenius). • Proton acceptors (Brønsted–Lowry).

  15. Strong Bases Strong bases are the soluble salts of hydroxide ion: • Alkali metals (Group I) • Calcium • Strontium • Barium Group II Notice that Ba(OH)2 is not very soluble in water but it is a strong base and a strong electrolyte This is the case because the mount of substance that dissolves dissociates almost Completely.

  16. Weak Bases

  17. Strong Electrolytes: • Soluble ionic compounds • Strong acids • Strong bases Weak Electrolytes: • Weak acids • Weak bases Nonelectrolytes: all other compounds

  18. Generally, when solutions of an acid and a base are combined, the products are a salt and water. HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) Soluble Salt Neutralization Reactions What is the complete ionic equation? What is the net ionic equation?

  19. When a strong acid reacts with a strong base, the net ionic equation is… H+ (aq) + Cl- (aq) + Na+ (aq) + OH- (aq)  Na+ (aq) + Cl- (aq) + H2O (l) Neutralization Reactions HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)

  20. 2HCl (aq) + Mg(OH)2(s)  MgCl2(aq) + 2H2O (l) Milky white suspension Consider the reaction between milk of magnesia and hydrochloric acid What is the complete ionic equation? What is the net ionic equation?

  21. These metathesis reactions do not give the product expected CaCO3 (s) + HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l) Acid-Base Reaction with Gas Formation NaHCO3 (aq) + HBr (aq) NaBr (aq) + CO2 (g) + H2O (l) SrSO3 (s) + 2 HI (aq) SrI2 (aq) + SO2 (g) + H2O (l) Na2S (aq) + H2SO4 (aq)  Na2SO4 (aq) + H2S (g)

  22. Autoionization of Water In pure water at 25 oC Is Pure Water an Acid or a Base or Neither?

  23. Is Pure Water an Acid or a Base or Neither? Water accepts a proton (base) Water donates a proton (acid) Water may act as an acid Water may act as a base Water may act as just a solvent (neither an acid nor a base)

  24. Acid-Base Reactions In an acid-base reaction, the acid donates a proton (H+) to the base.

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