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Good afternoon!

Good afternoon!. Lot’s of things to pick up today: Quiz Scantron Quiz version that you took Lab Sheet Final Study Guide Dry Erase Board Marker 10 minutes to look over missed quiz questions & answer the Catalyst. pH. (mm=119.02 g/ mol ). How does the molarity of H+ change?

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Good afternoon!

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  1. Good afternoon! • Lot’s of things to pick up today: • Quiz Scantron • Quiz version that you took • Lab Sheet • Final Study Guide • Dry Erase Board • Marker • 10 minutes to look over missed quiz questions & answer the Catalyst

  2. pH (mm=119.02 g/mol) • How does the molarity of H+ change? • How does the pH change? • As the concentration of H+ increases, pH __________________. • Why are the pH’s for test tubes 1 and 2 indicated as “<4”? • What is an Arrhenius acid and base? • What is a Bronsted-Lowry acid and base?

  3. pH • pH is a scale used to reflect the concentration of H+ ions! (but we really know that there are no free H+ ions, only hydronium (H30+) • Arrhenius acid is what? Bronsted-Lowry acid is what? • Remember that water is neutral: HOH <--> H+ + OH-

  4. Example Brønsted Acids and Bases: NH3 + HOH  NH4+ + OH- Here, H2O acts as a Brønsted acid by donating a proton to NH3 which acts as a Brønsted base.

  5. Neutralization Reaction • A reaction between an acid and a base where enough of each are combined so that the final solution is no longer acidic or basic, but neutral • What would be a product of a neutralization reaction? • We can use this fact to figure out the molarity of an acid or base solution with an unknown concentration by seeing how much of the other is required to neutralize it

  6. standard solution unknown solution Titration • Definition • Analytical method in which a standard solution is used to determine the concentration of an unknown solution. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  7. Buret stopcock Erlenmeyer flask

  8. Titration Vocabulary • Titrant • The substance added to the analyte in a titration (a standard solution) • Analyte • The substance being analyzed • Equivalence point • The point in a titration at which the quantity of titrant is exactly sufficient for stoichiometric reaction with the analyte.

  9. If the concentration of the titrant is known, then the unknown concentration of the analyte can be determined. Acid-Base Titration Titrant Analyte

  10. Buret Reading

  11. Acidic, basic, or neutral??

  12. The “perfect pink” for a titration with phenolphthalein

  13. point at which exactly enough reactant has been added for the solution to be neutralized and no more Indicator - changes color to indicate pH change pink pH Example… phenolphthalein is colorless in acid and pink in basic solution Endpoint = 7 colorless Volume base added

  14. Equivalence point (endpoint) • Point at which equal amounts of H3O+ and OH-are present in solution. • Determined by… • indicator color change • dramatic change in pH Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  15. Titration At endpoint... moles H3O+ = moles OH- Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  16. White Board Review! • Water • Solubility • Molarity • Dilutions • Acid and Base

  17. Problem #1 • What mass of CaCl2 (mm=110.98 g/mol) is required to make 1.25 L of a 0.250 M solution? • Answer: 34.7 g

  18. Problem #2 If 25 g of KCl is added to 50 g of water at 40°C, the solution would be: • Unsaturated • Saturated • Supersaturated

  19. Problem #3 • What characteristic of compounds like sugar and salt allow them to dissolve in water unlike oil? • Answer: they are polar, “like dissolves like”

  20. Problem #4 • What volume of of a a 5.00M Ca(NO3)2 solution is needed to prepare 465 mL of a 0.250 M Ca(NO3)2 solution? • Answer: 23.3 mL

  21. Problem #5 • Calculate the molarity of a solution prepared by dissolving 4.1 g of solid KBr(mm=119.02 g/mol) in enough water to make 1.10 L of solution • Answer: 0.031 M

  22. Problem #6 • Classify the following as an acid or base: • H3PO4 • NaOH • Ca(OH)2 • H2S

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