1 / 34

Solutions

Solutions. Honors Chemistry Snarrenberg 2012-2013. Catalyst: Tuesday 5/28. Think back to when you did the polarity demo in lab with Styrofoam and eco-peanuts… Think back to Chapter 3… What is a solution? What do you call the substance you’re dissolving?

lida
Télécharger la présentation

Solutions

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. Solutions Honors Chemistry Snarrenberg 2012-2013

  2. Catalyst: Tuesday 5/28 Think back to when you did the polarity demo in lab with Styrofoam and eco-peanuts… Think back to Chapter 3… • What is a solution? • What do you call the substance you’re dissolving? • What do you call the substance you’re dissolving it in? • How do you tell which is which? • What is an aqueous solution? • How do ionic compounds dissolve in water? • How do covalent compounds dissolve in water? • Can you think of a substance that doesn’t dissolve in water? What causes them to not dissolve?

  3. soap • After you eat fried chicken for dinner, (or pizza or steak or… anyone hungry yet?), and you’re asked to do the dishes, why do you have to use soap? • Why can’t you just use water? • But then how does the soap come off?

  4. Let’s look at the vocab  • Define the following using the words ‘solute’ and ‘solvent’ • Saturated solution • Unsaturated solution • Concentrated solution • Dilute solution • Demo time dudes!

  5. An aqueous solution containing 30 g of KCl in 50 g of water at 55°C is… • Unsaturated • Saturated • Supersaturated • An aqueous solution containing 5 g of NaNO3 in 10 g of water at STP is… • Unsaturated • Saturated • Supersaturated • An aqueous solution containing 25 g of NaNO3 in 50 g of water at72°C is… • Unsaturated • Saturated • Supersaturated

  6. Demo questions • Is the solution saturated or unsaturated? • Is the solution concentrated or dilute? • What happens as the solution is heated? • ..but wait, wasn’t it saturated already? • What happens as the solution cools? • What happens when a crystal of solid is added?

  7. Comparing flasks • Draw a qualitative picture to represent the concentration in each flask. • How could you quantify the concentration in the flasks?

  8. Which salt has the highest solubility at STP? • Which salt has the lowest solubility at STP? • If you have 50 g of water, how many grams of lead (II) nitrate will make a saturated solution?

  9. Catalyst: Thu 5/30 HW Tonight: 38, 40, 50 • How many grams of sodium acetate can dissolve in 100 g of water at 25°C? • How many grams of sodium acetate can dissolve in 50 g of water at 25°C? • At around what temperature can I dissolve 140 g of sodium acetate to make a saturated solution?

  10. Quantifying it! • How do you quantify the concentration of a solution? • Molarity! (M) – mol/L • 1.0 molar solution, written as 1.0 M, contains 1.0 mols of solute per liter of solution

  11. Calculating molarity • What is the molarity of a solution containing 11.5 g of NaOH with a volume of 1.50 L? • M = moles of solute liters of solution • M = 0.288 molNaOH = 0.192 M NaOH 1.50 L solution

  12. Preparation of a standard solution Standard solution: a solution whose concentration is accurately known

  13. Calculating Molarity • 0.105 M • 0.00061 M • 0.61 M • Calculate the molarity of a solution prepared by dissolving 15.6 g of solid KBr in enough water to make 1.25 L of solution • Calculate the molarity of a solution prepared by dissolving 250.0 g of solid Ca(NO3)2 in enough water to make 2500 mL of solution

  14. POGIL Question A student correctly determines that 17.1 grams of sucrose are needed to make 50 mL of a 1 M sucrose solution. When making this solution in lab, the student measured 50 mL of water and massed 17.1 grams of sucrose. The student then mixed the two together into a new beaker. The student’s resulting solution was not 1 M sucrose as intended. After the student mixed sucrose and water, the resulting solution was poured into a graduated cylinder and it read 62 mL. • What part of the molarity equation did the student overlook when mixing the solution? • What steps should the student take in lab to correctly prepare the 1 M solution?

  15. Note on Molarity • How many mols of NaCl are in a 1.0 M NaCl solution? • …actually, there are no NaCl units in a NaCl solution, only Na+ ions and Cl- ions • 1.0 mols Na+ === 1.0 M Na+ • 1.0 molsCl- === 1.0 M Cl- • Net ionic equations

  16. Concentration of ions in solution • 2.40 M Na+ • 1.20 M SO42- • 1.50 M K+ • 0.750 M CrO42- • 1.20 M Na2SO4 • 0.750 M K2CrO4

  17. Calculating # mols from molarity • Molarity has a complex unit (mol/L) and can be used as a conversion factor! (You must be so excited XD) • How many mols of Ag+ ions are in 25 mL of a 0.75 M AgNO3 solution? • 0.75 M AgNO3 = 0.75 M Ag+

  18. You try  • 1.47 x 10-2mol Na+ • 4.41 x 10-2mol Na+ • How many moles of Na+ ions are present in 42.0 mL of a 0.350 M NaCl solution? • How many mols of Na+ ions are present in 42.0 mL of a 0.350 M Na3PO4 solution?

  19. Calculating mass from molarity • 31.9 g • 41.3 g • What mass of NaNO3 is required to make 2.50 L of 0.150 M solution of NaNO3? • What mass of (NH4)2SO4 is required to make 1.25 L of a 0.250 M solution of (NH4)2SO4?

  20. HW Check • #54: the new concentration of solute is half the original • #58: 0.541 L • #60: 0.13 M • #62: 10.3 mL • Dilutions Review: key words to watch out for that indicate a dilutions problem with M1V1=M2V2 • A change in molarity of the solutions with the same solute • Concentrated / Dilute • New solution / original solution

  21. HW Review

  22. Catalyst: Monday 6/2 • Draw a stoichiometry map (remember, the center link is always Mol A <--> Mol B) to include molarity. Think about all the units you can come from and go to. • HW: 66, 67, 68 (Ch. 15) • Quiz Thursday on Solubility (graph), Molarity, Dilutions, and Solutions Stoich

  23. Stoichiometry Review Propane, used in gas barbecue grills, burns in oxygen according to the following balanced chemical equation: C3H8(g) + 5O2(g)  3CO2 (g) 4H2O Calculate the mass in grams of water vapor produced if 3.11 mol of propane is burned. ANSWER: 224 g

  24. Catalyst: Monday 6/2 • Draw a stoichiometry map (remember, the center link is always Mol A <--> Mol B) to include molarity. Think about all the units you can come from and go to. • What if you started with L of a solution or you needed to go to L or of a solution? Now add a new bridge. • If we are dealing with reactions where the reactants are aqueous solutions, what TYPE of reaction are we talking about? (oooh throw back)

  25. Solutions Stoichiometry#1silver nitrate + potassium chloride  ?

  26. Solutions Stoichiometry #1 • If I mixed 2 mL of 1.5 M silver nitrate with excess potassium chloride, how many grams of solid silver chloride was I able to produce? Answer: 0.43 g

  27. Solutions Stoichiometry #3 Limiting Reactant Problem! Calculate the mass of the white solid CaCO3 that forms when 25.0 mL of a 0.100 M Ca(NO3)2 solution is mixed with 20.0 mL of a 0.150 M Na2CO3 solution. Answer: 0.250 g CaCO3

  28. Announcements • Quiz Thursday on Solubility (graph), Molarity, Dilutions, and Solutions Stoich • HW: 15.7 Notes& #65

  29. Solutions Stoich #4aluminum + copper (II) chloride  ? HW Answers: • #66 – 0.523 g • #67 – 0.976 g PbCrO4 • #68 – 0.300 g

  30. Brainstorm • What pieces of information do you need to find the molarity of the copper (II) chloride solution? • What tools in your toolbox can you use to get those pieces of information? (Hint: one you can find directly, the other must be found indirectly, i.e. through calculation)

  31. Some info… • Volume of CuCl2 solution used: 20.0 mL • Mass of Al before the reaction: 0.59 g • Aluminum is the excess reactant!

  32. % Error Calculation • The actual molarity of the CuCl2 solution was 0.65. What was the percent error?

  33. Try this one… Solutions Stoich #5 One way to determine the amount of chloride ion in a a water sample is to titrate the sample of standard AgNO3 solution to produce solid AgCl. Ag+(aq) + Cl-(aq)  AgCl(s) If a 25.0 mL water sample requires 27.2 mL of 0.104 M AgNO3 in such a titration, what is the concentration of Cl- in the sample? Answer: 0.113 M

  34. Solutions Stoichiometry #2 • Calculate the mass of sodium iodide that must be added to 425.0 mL of a 0.100 M lead (II) nitrate solution to precipitate all of the lead (II) ions as lead (II) iodide. Answer: 12.7 g NaI

More Related