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Mixtures & Solutions

Mixtures & Solutions. Chapter 14. What is a Solution?. Which of the following are solutions? Bronze Coffee Gasoline Air Helium Concrete. What is a Solution?. A solution is a homogeneous, single phase mixture. It can be a gas, liquid, or solid. Solvent, Solute – There is a Difference.

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Mixtures & Solutions

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  1. Mixtures & Solutions Chapter 14

  2. What is a Solution? • Which of the following are solutions? Bronze Coffee Gasoline Air Helium Concrete

  3. What is a Solution? • A solution is a homogeneous, single phase mixture. • It can be a gas, liquid, or solid.

  4. Solvent, Solute – There is a Difference • The solute dissolves in the solvent. • Sugar Water • The water is the solvent • The sugar is the solute • Salt Water • The water is the solvent. • The salt is the solute.

  5. Solvent, Solute – There is a Difference • Your textbook says that the substance present in the largest amount is the solvent and this is true most of the time. • If a solid is added to a liquid and the resulting solution is liquid, the liquid is considered to be the solvent even is there is more of the solid. • Example, you can dissolve 109 grams of NaOH in 100 grams of water. The result is a liquid solution and water would be the solvent.

  6. SIX TYPES OF SOLUTION SOLUTE SOLVENT EXAMPLE solid liquid liquid liquid gas liquid gas gas solid solid liquid solid Note: the solution is in the same phase as the solvent.

  7. Heterogeneous Mixtures • A heterogeneous mixture is a mixture that does not have a uniform composition and in which the individual substances remain distinct. • Suspensionsare mixtures containing particles that settle out if left undisturbed.

  8. Colloids are heterogeneous mixtures of intermediate sized particles (between 1 nm and 1000 nm) and do not settle out. • The most abundant substance in a mixture is the dispersion medium. • Colloids are categorized according to the phases of their particles.

  9. Solution Concentrations • The concentrationof a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution. • Concentration can be described as concentrated or dilute.

  10. In order to maintain a sodium chloride concentration similar to ocean water, an aquarium must contain 3.6 g NaCl per 100.0 g of water. What is the percent by mass of NaCl in the solution?

  11. What is the percent by Mass of NaHCO3 in a solution containing 20.0 g of NaHCO3 dissolved in 600 mL of water?

  12. The percent by mass of calcium chloride in a solution is found to be 2.65 %. If 50.0 g of calcium chloride is used, what is the mass of the solution?

  13. Molarityis the number of moles of solute dissolved per liter of solution.

  14. Preparation of a standard aqueous solution.

  15. TYPE ONE PROBLEMS Given  Moles  Desired Unit 1. What is the volume, in ml, of 2M Na2SO4 containing 20.0g of the solute? 2. What mass of ammonia, NH3, is contained in 300.ml of 2.75M NH3. 3. 40.0 g of Sodium Hydroxide, NaOH, are dissolved into 200.ml of solution. What is the resultant molarity?

  16. PROBLEM SET • What volume of 2.25 M H2SO4 contains 9.81g? • What is the mass of CaCl2 in 100.0 ml of 1.75M CaCl2? • 19.6 g of H3PO4 are dissolved in 500.0 ml of solution. What is the resultant molarity?

  17. TYPE TWO PROBLEMS Diluting solutions with water. Dilution equation: M1V1 = M2V2 1. 15.0ml of water are added to 30.0ml of 2.00M KCl. What is the new molarity? 2. How much water must be added to 40.0ml of 2.75M Na2S to reduce it to 2.50M?

  18. What volume of water must be added to reduce 20.0ml of 1.5M HCl to 1.0M HCl? • What must 30.0 cm3 of 2.75 M KBr be diluted to reduce it to 2.50M? • 15.0ml of water are added to 30.0ml of 3.00M HBr. What is the new molarity?

  19. TYPE THREE PROBLEMS Mixing solutions of different concentrations MV = MFVF 1. 10.0ml of 2.00M KCl, 35.0ml of 1.25M KCl, and 50.0ml of 3.75M KCl are mixed. What is the new molarity? 2. What volume of 2.00M HCl must be mixed with 20.0ml of 3.25M HCl to reduce it to 3.00M HCl?

  20. where XA and XB represent mole fractions of each substance • Mole fractionis the ratio of the number of moles of solute in solution to the total number of moles of solute and solvent.

  21. Suppose a hydrochloric acid solution contains 36 g of HCl and 64 g of water. What is the mole fraction present of each?

  22. What will dissolve, what won’t? • Solvation is the process of surrounding solute particles with solvent particles to form a solution. • Solvation in water is called hydration. • The attraction between dipoles of a water molecule and the ions of a crystal are greater than the attraction among ions of a crystal.

  23. Polar water molecules interacting with positive and negative ions of a salt.

  24. The ethanol molecule contains a polar O—H bond.

  25. The polar water molecule interacts strongly with the polar O—H bond in ethanol.

  26. Structure of common table sugar.

  27. A molecule typical of those found in petroleum.

  28. SIMILA SIMILIBUS SOLVUNTUR This statement simply translates into “like dissolves like” a. Polar solvents dissolve polar and ionic solutes.

  29. An oil layer floating on water.

  30. How much? How fast? • Solubility • Saturated, unsaturated, supersaturated. • What affects the RATE at which a solid dissolves in a solvent?

  31. Solubility - the amount of solute in g that saturates 100ml of water. Factors affecting solubility a. Temperature b. Surface Area c. Agitation-stirring or shaking

  32. Unsaturated solution - less than the maximum amount of solute is dissolved. Saturated solution - the maximum amount of solute is dissolved. Supersaturated solution - more than the maximum amount of solute is dissolved. a. This is unstable. b. This can be brought back to the saturated state by either scratching the surface of the container with a file or adding a crystal of the solute.

  33. SATURATED SOLUTIONS These are solutions that have the maximum amount of solute dissolved in the solvent. A saturated solution is an equilibrium state. a. How is it recognized? b. What are the conditions? c. How is it defined on the molecular level?

  34. Factors that affect the rate of dissolving for a solid solute in aqueous solution. a. Stirring b. Temperature c. Surface Area

  35. GASES DISSOLVED IN AQUEOUS SOLUTION Factors affecting solubility of a gas in a liquid a. Temperature b. Pressure HENRY’S LAW - the solubility, S, of a gas is directly proportional to the pressure exerted by the gas above or on the liquid.

  36. Henry’s Law

  37. PROBLEM SET • A gas has a solubility of 0.0123 mol/liter at 1.18 atm of pressure. What is the solubility at 355 atm of pressure? • A gas has a solubility of 1.235 g/liter at 4550 mm Hg. What is the solubility at 760 mm Hg?

  38. Colligative propertiesare physical properties of solutions that are affected by the number of particles but not by the identity of dissolved solute particles.

  39. Ionic compounds are electrolytes because they dissociate in water to form a solution that conducts electricity. • Some molecular compounds are also electrolytes.

  40. Vapor Pressure Lowering • Adding a nonvolatile solute to a solvent lowers the solvent’s vapor pressure. • When a solute is present, a mixture of solvent and solute occupies the surface area, and fewer particles enter the gaseous state.

  41. The greater the number of solute particles, the lower the vapor pressure. • Vapor pressure lowering is due to the number of solute particles in solution and is a colligative property of solutions.

  42. Boiling Point Elevation • When a nonvolatile solute lowers the vapor pressure of a solvent, the boiling point is also affected. • More heat is needed to supply additional kinetic energy to raise the vapor pressure to atmospheric pressure.

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