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Solutions and Acids/Bases

Solutions and Acids/Bases. Chem Catalyst Bearly Alive. Five gummy bears have been placed overnight in five different aqueous sugar solutions. Each solution contains a different amount of dissolved sugar.

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Solutions and Acids/Bases

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  1. Solutions and Acids/Bases

  2. Chem CatalystBearly Alive • Five gummy bears have been placed overnight in five different aqueous sugar solutions. Each solution contains a different amount of dissolved sugar. • Which solution do you think has the greatest amount of sugar in it? Explain your reasoning. • What do you think caused the bears to change size?

  3. Gummy bear picture 1

  4. Gummy Bears picture 2

  5. Gummy Bears picture 3

  6. Chem Catalyst - Recap • Which solution do you think has the greatest amount of sugar in it? Explain your reasoning. • What do you think caused the bears to change size?

  7. Chem CatalystKool-Aid Lab • How many grams of sugar do you think you need to dissolve to make Kool-Aid according to the recipe? (Hint:it’s about 1 cup) • If you discovered an even better way to make Kool-Aid using only sugar, water, and the Kool-Aid powder, how would you tell someone else to make the exact same recipe?

  8. Chem CatalystBearly Alive day 2 Suppose you take 100 mL of water and dissolve 33.0 grams of sugar, C12H22O11 in it. The final volume is now 125 mL. 1.) Calculate the volume in Liters. 2.) Calculate the moles of sugar that is dissolved in the solution.

  9. Calculating concentrations

  10. Definitions • Solute – Stuff that dissolves (sugar, salt, etc) • Solvent – What does the dissolving (usually water) • Solution – The solute dissolved in the solvent (sugar water). • Saturated solution: A solution that contains the maximum amount of solute for a given amount of solvent.

  11. Concentration • For solutions, we measure the concentration of solute for every liter of solution. moles L • This concentration also is called the molarity of a solution.

  12. ChemCatalyst • We saw yesterday that the concentration of Kool-Aid based on the package instructions was 0.31 M. 1.) A can of Coke has 39 g of sugar dissolved in 0.355 L of solution. The molar mass of sugar (sucrose) is 342.34 g = 1 mole sucrose. What is the molarity of Coke? 2.) Which is more concentrated – a can of Coke or Kool-Aid? How do you know?

  13. Check-in • Suppose 10.0 g of salt, NaCl, are dissolved in 0.50 L of water. What is the molarity of the solution?

  14. Chem Catalyst½ day Thionin demo 1.) What do you think causes the changes you observe in the reaction you are about to see? 2.) How could you test your hypothesis?

  15. Chem Catalyst 1.) What has been the most frustrating part of this project? How could this part be less frustrating? 2.) What have you learned the most about from this project? 3.) Do you think learning through projects is better than the traditional classwork and test approach? Why?

  16. Chem Catalyst Calculate the concentration (molarity) of a solution that has 42 grams of NaCl in 600 ml of solution. Show your work and units. • First, convert grams NaCl  moles • Convert ml to L • Calculate the molarity, M

  17. Chem Catalyst Your boss asks you to prepare a 1.6 M solution of KCl, using 23.4 grams of KCl. How many liters of water should you use to make this solution? • Identify givens, and unknown • Which molarity equation is useful? • Convert grams KCl  moles • Calculate!

  18. Chem CatalystDrop In • Examine the gummy bear in sugar solution that was prepared in class yesterday. • What does the gummy bear’s appearance suggest about the solution? • Is the solution saturated? Why or why not? • Imagine that you have 1 L of a 2.0 M sugar solution in a large container. You pour out 100 mL into a beaker. • Did the concentration in the large container change? • Did the number of moles of sugar in the large container change?

  19. Example Problem (old worksheet) 9 inches #Dots = Area = Concentration = 7 inches

  20. Particle View #1

  21. Solution Concentrations

  22. Concentration and “molarity” • Molarity describes the concentration of a solution. It is measured in: moles of solute -------------------- = M L of solution • The terms “molarity” and “concentration” are usually interchangeable.

  23. Word descriptions • Describe the following without using the words “per”, “over” or “divided by”. • I have a 3.5 mol/L solution of sodium chloride. • I have a 2.7 M solution of calcium chloride.

  24. Check-In • How many moles of sugar, C12H22O11, are in 52 mL of a 0.50 M solution? • How many moles of sugar, C12H22O11, are in 26 mL of a 0.50 M solution?

  25. Chem Catalyst • What is the concentration of a solution with 4.3 moles of sugar in 1 liter of solution? • What is the molarity of a solution of 2.6 moles of sugar in 0.6 liters of solution? • What is the molarity of a solution of 25.0 grams of NaCl in 400 mL of solution?

  26. Chem Catalyst • What volume of solution is necessary to create a 2.0 M solution of NaCl with 5.84 g of NaCl? • Use the equation for molarity and solve for “L”

  27. Molarity Question • A student just spent all hour in chemistry trying to create a 1.8 M solution of NaCl. She calculated how many moles of NaCl were needed, converted to grams, and dissolved in the right amount of water. Someone walked in front of her with her solution, causing her to spill half of it on the floor. Now she only has some of her solution left in the beaker. • Is the remaining solution still the same molarity? Why or why not?

  28. Chem CatalystMaking Solutions GET PERIODIC TABLE & CALCULATOR!!! 1.) You dissolve 38.4 g of sodium nitrate (NaNO3) in enough water to make a 300 mL solution. What is the molarity (molar concentration) of the solution you created? Given: Unknown: Convert g  moles Convert mL  L Use equation for molarity to solve

  29. Answers to molarity bucket Q’s 9.) 31.5 g 10.) 25.65 g 11.) 36.96 g 12.) 147.6 g 1.) 0.636 M 2.) 0.348 M 3.) 0.973 M 4.) 18.07 M 5.) 1.47 M 6.) 0.767 M 7.) 4.13 M 8.) 1.02 M

  30. Chem CatalystMaking Solutions GET PERIODIC TABLE & CALCULATOR!!! 1.) How many grams of salt (NaCl) should you dissolve if you want to make a 250 mL solution of 3.0 M NaCl? Given: Unknown: Convert mL  L Use correct equation to find moles of NaCl Find the molar mass of NaCl Convert moles of NaCl  grams of NaCl

  31. Solutions of NaCl – Lab practical • 50 mL of… • 0.6M • 1.2M • 1.8M • 2.4M • 0.4M • 0.8M • 0.9M • 1.8M • 100 mL of… • 0.6M • 1.2M • 1.8M • 2.4M • 0.4M • 0.8M • 0.9M • 1.8M

  32. Molar concentration [NaNO3] = “concentration of NaNO3” [NaNO3] =

  33. Practice problem • What final volume would be needed in order to prepare a 0.70 M solution from 12.5 g of NaNO3 (s)?

  34. Rearranging equations • Suppose you have the generic equation: B A = ----- C

  35. Chem Catalyst • Three particles of strontium nitrate, Sr(NO3)2 are dissolved in water. • Draw ONE particle(molecule) of strontium nitrate • Now draw the other two • Because this compound is ionic, it will break into different ions. What will it break into?

  36. Dissolving strontium nitrate Before dissolving After dissolving

  37. Mole ratios (moles within moles); problem #1 on WS 1 mole Sr(NO3)2 =

  38. Chem Catalyst 1.) What chemical substance do you think is in fire extinguishers? 2.) How do fire extinguishers put out fires? 3.) We are going to make mini-fire extinguishers tomorrow. How do you think we will produce the fire extinguisher gas?

  39. Chem Catalyst Yesterday, each group found out how many milliliters of CO2 gas they need to create for their mini fire extinguishers. 1.) How do you think you could collect the correct amount of gas? How are you going to capture the gas that is created and be able to measure it?

  40. Chem Catalyst • Many products are advertised on TV with the promise of reducing acid indigestion. • What is acid indigestion? • What does acid have to do with your stomach? • How do you think acid “reducers” like TUMS work?

  41. pH Scale pH scale: A number line from 0 - 14. The numbers correspond with indicator colors. 0 7 14 Acid Neutral Base

  42. Notes • Indicators: A set of substances that respond to acids or bases with vivid color changes. • Examples of indicators: • Red cabbage juice • Litmus paper • Universal indicator

  43. Notes • Acids < 7 on universal indicator scale Taste sour (lemon juice) React with calcium carbonate (chalk, antacid) • Bases > 7 on universal indicator scale Taste bitter (soap) and feel slippery Do not react with calcium carbonate • Neutral substances At or near 7 on universal indicator scale

  44. Observations • Acids: • Bases:

  45. Making sense • What happens when the acid in your stomach, HCl, reacts with an antacid like calcium carbonate, CaCO3?

  46. Chem Catalyst • An unknown solution turns purple when universal indicator is added. It also does not react with calcium carbonate. • Is the unknown solution an acid, base, or neutral substance? Explain.

  47. What do we know about acidic, basic and neutral substances so far? Acids Bases Neutral

  48. Making Sense • Acids are things that add H+ to solution. • Bases are substances that add OH- to solution. • Neutral substances do not add H+ or OH- to solution.

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