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Announcements

Announcements. EXAM #1 ANSWER KEY POSTED OWL: CHAPTER 4 PART 1 HOMEWORK EXAM GRADES POSTED (LEFT SIDE “COURSE GRADES” LINK). Solution Concentration. Solution Solute Solvent Concentration Qualitative Dilute Concentrated Quantitative Molarity=# moles of solute per 1L of solution.

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Announcements

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  1. Announcements EXAM #1 ANSWER KEY POSTED OWL: CHAPTER 4 PART 1 HOMEWORK EXAM GRADES POSTED (LEFT SIDE “COURSE GRADES” LINK)

  2. Solution Concentration • Solution • Solute • Solvent • Concentration • Qualitative • Dilute • Concentrated • Quantitative • Molarity=# moles of solute per 1L of solution

  3. What do goldfish have to do with concentration?

  4. Solution Concentration Examples • How many moles of NH3 are in 575mL of 0.12mol/L solution? • A 0.56M solution of NH3 contains 22 mol NH3. How many Liters of solution are there? What you “have” Conversion factor

  5. What volume of a 0.23M solution of K2SO4 contains 0.50 moles? • 0.115L • 0.115mL • 2.174L • 2.174mL 0

  6. How would you make 250mL of 1.00M NH3 from 15M NH3? • Take 16.7mL of 15M NH3 and dilute it to 250mL with water • Take 60mL of 15M NH3 and dilute it to 250mL with water • Take 0.0167mL of 15M NH3 and dilute it to 250mL with water • Take 3.75mL of 15M NH3 and dilute it to 250mL with water 30

  7. Stoichiometry in Solution Grams or mL reactant A Grams or mL reactant B Molar mass or Solution concentration Molar mass or Solution concentration Moles reactant A Moles reactant B Balanced equation and Stoichiometry

  8. Titration Example- Part 1 GOAL: To determine the molar mass of an unknown acid (H2A) H2A + 2NaOH  Na2A + 2H2O • Standardizing an NaOH solution using a “primary standard” A solution of sodium hydroxide is “standardized” by titration using solid oxalic acid, H2C2O4, as the acid. It is found that 24.5 mL of the NaOH solution is needed to react completely with 2.05 g of oxalic acid. What is the concentration of the NaOH solution? H2C2O4(aq) + 2 NaOH  2 H2O(l) + Na2C2O4(aq)

  9. Titration Example- Part 2 • Determining the molar mass of an unknown diprotic acid The NaOH solution above was used to titrate an acid of unknown formula, but known to be diprotic: H2A, where we don’t know what “A” is. A 1.046 gram sample of the unknown acid is titrated using 31.4 mL of the NaOH solution. What is the molar mass of H2A? H2A(aq) + 2 NaOH  2 H2O(l) + Na2A(aq)

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