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CH 13 Solutions!

CH 13 Solutions!. Solution = stable homogeneous mixture; has the same composition throughout, does not settle out, and particles are dissolved; can’t distinguish phases under a microscope The solute is what gets dissolved and the solvent is what does the dissolving.

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CH 13 Solutions!

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  1. CH 13 Solutions!

  2. Solution = stable homogeneous mixture; has the same composition throughout, does not settle out, and particles are dissolved; can’t distinguish phases under a microscope • The solute is what gets dissolved and the solvent is what does the dissolving. • In salt water the salt is the solute and water is the solvent.

  3. Not all solutions are liquids only: • Solid in a liquid = salt water • Gas in a liquid = soda pop (carbon dioxide in water) or in a lake dissolved oxygen in water. • Gas in Gas = Air around us is mixture of mainly nitrogen and oxygen • Liquid in liquid = alcohol in water • Solid in a solid = these are also known as alloys.

  4. Ex. Liquid in liquid mixture

  5. FYI Other types of alcohol are not safe to drink. They can be toxic and even fatal is consumed. They include: • Butyl alcohol, or butanol. This type of alcohol, derived from butane, is commonly used in products such as adhesives and varnishes.

  6. FYI • Methyl alcohol, also known as methanol or wood alcohol. It is used in the manufacture of formaldehyde and as industrial solvent. During Prohibition wood alcohol gained notoriety as a mixing agent with ethyl alcohol to make liquor. • Several people became blind after drinking this toxic mixture, as methyl alcohol causes swelling of the optic nerve, an irreversible condition.

  7. FYI • Isopropyl alcohol, also known as rubbing alcohol, is a common household product. It is used as a disinfectant and as an ingredient in cologne and after-shave lotion. • Ethylene glycol, also known as antifreeze, is the most harmful type of alcohol. It should never be consumed, as it is deadly.

  8. Examples of Alloys: Brass – copper + zinc Bronze – copper + tin/aluminum Steel – iron, carbon + others White gold – gold + Ni + Pd Wrought iron – iron + carbon

  9. 13.2 Concentration & Molarity • In a solution, the solute is distributed evenly throughout the solvent. • Any part of the solution has the same solute to solvent ratio or concentration • Concentrations can be expressed in many forms Ex. molarity, ppm, molality

  10. Parts per million (ppm) = gram solute per one million grams solvent; used in measurements such as pollution that involve very low concentrations 1 mg/L = 1 ppm Ex. Lead in drinking water

  11. ppm = gram solute 1 000 000 g solution • “Parts” are measured by mass

  12. Sample Problem A p. 461 A chemical analysis shows that there are 2.2 mg of lead in exactly 500 g of a water sample (solution). Convert to ppm. (grams solute/one million grams solution) Convert mg to grams 2.2 mg x = Divide by 500 grams to get the grams (parts) in 1 gram of water. Multiply by 1 000 000 to get the amount of grams in 1 000 000 g water. 2.2 x 10-3 g of Pb x 1 000 000 parts = 4.4 ppm Pb in the water 500 g H2O 1 million • 4.4 grams of lead for every 1 000 000 grams of solution • 0.000 004 4 grams of lead for every 1 gram of solution 1 gram 1000 mg 2.2 x 10-3 g of Pb

  13. Practice Problems #1-7 p. 461 • Helium gas, 3.0 x 10-4g, is dissolved in 200.0g of water. Express in ppm. 3.0 x 10-4g He 200.0 g H20 x 1 000 000 parts 1 million = 1.5 ppm

  14. Practice Problems #1-7 p. 461 2. A sample of 300.0g of drinking water is found to contain 38 mg Pb. Express in ppm. 38 mg Pb x 1 g = 0.038 g 1000 mg 0.038 g Pb 300.0 g H20 x 1 000 000 parts 1 million = 126.6 = 130 ppm

  15. Practice Problems #1-7 p. 461 3. A solution of lead sulfate contains 0.425 grams of lead sulfate in 100.0 grams of water. Express in ppm. 0.425 gPbSO4 100.0 g H20 x 1 000 000 parts 1 million = 4250 ppm

  16. Practice Problems #1-7 p. 461 4. A 900.0 g sample of sea water is found to contain 6.7 x 10-3 g Zn. Express in ppm. 6.7 x 10-3 g Zn. 900.0 g H20 x 1 000 000 parts 1 million = 7.4 ppm

  17. Practice Problems #1-7 p. 461 5. A 365.0 gram sample of water contains 23 mg Au. Express in ppm. 23 mg Au x 1 g = 0.023 g 1000 mg 0.023 g Au 365.0 g H20 x 1 000 000 parts 1 million = 63 ppm

  18. Practice Problems #1-7 p. 461 6. A 650.0 g hard-water sample contains 101 mg Ca. Express in ppm. 101 mg Ca x 1 g = 0.101 g 1000 mg 0.101 g Ca 650.0 g H20 x 1 000 000 parts 1 million = 155 ppm

  19. Practice Problems #1-7 p. 461 7. An 870.0 g river water sample contains 2.0 mg Cd. Express in ppm. 2.0 mg Cd x 1 g = 0.0020 g 1000 mg 0.0020 g Cd 870.0 g H20 x 1 000 000 parts 1 million = 2.3 ppm

  20. Which of the following would be the most concentrated solution? (Hint: density of water 1g/1mL) • 200 g of C12H22O11 in 1 kg of water • 1000 ppm of C12H22O11 in water • 1500 ppm of C12H22O11 in water • 1 mol of C12H22O11 in 1 L of solution A. 200 grams C12H22O11 x 1000 0000 = 200 000 ppm 1000 grams water 1 million D. 1 mol = 12(12) + 22(1) + 11(16) = 342 g SO 1 L x 1000 mL x 1 g = 1000 g 1 L 1 mL 342 grams C12H22O11 x 1000 0000 = 342 000 ppm 1000 grams water 1 million

  21. Application: p. 489 # 37-40

  22. Molarity • Allows chemists to describe the number of solute particles in a volume of total solution (not just solvent) Molarity = moles of solute dissolved in a liter of solution M = mol/L (read “moles per liter” or “molar”)

  23. [ ] = molarity (in aqueous solution) [CuSO4] = 0.5 M The molarity of copper sulfate is 0.5 M or moles per liter. [NaNO3] = 1.0 M The molarity of sodium nitrate is 1.0M. Also called a 1 molar solution.

  24. Sample B p.465Calculating Molarity Molarity = moles of solute liters of solution What is the molarity of a potassium chloride solution that has a volume of 400.0 mL and contains 85.0g KCl?

  25. Step 1 Convert solute to moles. 85.0 g KCl x 1 mol = 1.14 mol KCl 74.55 g KCl Step 2 Convert solution to liters. 400.0 mL x 1L = 0.400 L 1000 mL Step 3 Divide moles by liters. 1.14 mol KCl = 2.85 M KCl 0.400 L

  26. Practice p. 465 #1-7 Calculate molarity of the given solutions. • Vinegar contains 5.0g of acetic acid, CH3COOH, in 100.0 mL of solution. 5.0 g x 1 mol = 0.083 mol acetic acid 60 g 0.083 mol = 0.83 M acetic acid solution 0.100 L

  27. 2. If 18.25g HCl is dissolved in enough water to make 500.0mL of solution, what is the molarity of the solution? 18.25 g x 1 mol = 0.5005 mol HCl 36.46g 0.5005 mol = 1.001 M hydrochloric acid solution 0.500 L

  28. 3. If 20.0 g H2SO4 is dissolved in enough water to make 250.0mL of solution, what is the molarity of the solution? 20.0 g x 1 mol = 0.204 mol 98.09g 0.204 mol = 0.816 M sulfuric acid solution 0.2500 L

  29. 4. A solution of AgNO3 contains 29.66 g of solute in 100.0 mL of solution. What is the molarity of the solution? 29.66 g x 1 mol = 0.175 mol 169.9g 0.175 mol = 1.75 M silver nitrate solution 0.1000 L

  30. 5. A solution of barium hydroxide, Ba(OH)2, contains 4.285 g of solute in 100.0 mL of solution. What is the molarity of the solution? 4.285 g x 1 mol = 0.0250 mol 171.35g 0.0250 mol = 0.2501 M barium hydroxide solution 0.1000 L

  31. 6. What mass of KBr is present in 25 mL of a 0.85 M solution of potassium bromide? x mol = 0.85M x = 0.85 mol X 0.025 L = 0.021 mol 0.025L L 0.021 mol KBr x 119 g = 2.5 g KBr 1 mol

  32. 7. If all of the water in 430.0 mL of 0.45 M NaCl solution evaporates, what mass of NaCl will remain? x mol = 0.45M x = 0.45 mol X 0.4300 L = 0.19 mol 0.4300 L L 0.19 mol NaCl x 58.44 g = 11 g NaCl 1 mol

  33. Application: p. 489 # 41-45 9.2 Review p. 467 # 2,4-9

  34. Preparing a Solution of Specified Molarity If you add 1.000 mol solute to 1.000 L of solution, the molarity would NOT be 1.000M. Why not??? • The added solute would change the total volume of the solution. • Molarity would be = 1 mol = 0.83M 1.2 L

  35. Preparing 1.000L of solution (p. 463) • Convert moles to mass using molar mass. • Measure amount needed in grams. • Add small amount water (solvent) to beaker and dissolve. • Pour into 1.000 L volumetric flask. • Rinse beaker and pour into flask. • Stopper flask & swirl. • Carefully add water to 1.000L mark on flask. • Stopper & invert at least 10 times.

  36. Why don’t you fill with water to the 1000 mL mark and then add solute? Because then the total volume of the solution will be greater than 1000 mL.

  37. Video Application: Molarity Lab

  38. Dilution = adding more solvent to a solution so that the concentration of the solute becomes lower.  • The total number of solute particles in the solution remains the same after dilution, but the volume of the solution becomes greater, resulting in a lowermolarity, ppm, mg/L, or % concentration. 

  39. Dilution video • Dilution – Preparation of Solutions

  40. END OF PART 1 NOTES

  41. 13.3 Solubility & Dissolving Solubility = ability of one substance to dissolve into another at a given temperature & pressure.

  42. Dissolving Liquids Miscible = 2 liquids that are able to dissolve into each other Immiscible = do not mix; form 2 layers upon settling, droplets when mixed These liquids are immiscible. Nonpolar molecules form droplets

  43. Two mutually immiscible liquids in a cylinder are heated with a light bulb. • The density of the liquids change as they are heated and cooled.

  44. DISSOLVING SOLIDS Solvation (aka dissolution) = process of breaking apart the crystal lattice of ionic solids Hydration = as ions dissolve in a solvent they spread out and become surrounded by solvent molecules. • Water molecular are polar • Partially positive hydrogen surrounds neg. ions • Partially negative oxygen surrounds pos. ions Ex. Video Dissolution of KMnO4

  45. Solubility depends on • Nature of solute & solvent molecules • Surface area • Temperature • Pressure (for gases only)

  46. 1. Nature of Solute/Solvent - POLARITY “Like dissolves like” • A polar covalent solvent will dissolve ionic solutes and other polar covalent solutes • A nonpolar covalent solvent will dissolve nonpolar solutes Video • Why no discussion of ionic solvents?

  47. Water is a common example of a polar solvent. • Carbon tetrachloride is a common example of a nonpolar solvent – unequal sharing geometrically cancels/balances immiscible

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