1 / 26

Solutions

Solutions. Chapter 17-18. Solutions. Homogeneous mixture of two or more substances in a single phase Solute: substance being dissolved Solvent: dissolving medium- substance doing the dissolving; if in doubt, substance that occurs in largest amount

myrna
Download Presentation

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 Chapter 17-18

  2. Solutions • Homogeneous mixture of two or more substances in a single phase • Solute: substance being dissolved • Solvent: dissolving medium- substance doing the dissolving; if in doubt, substance that occurs in largest amount • Aqueous solution (aq): solution where water is solvent

  3. Examples of Solutions

  4. Generic Terms • By soluble, we mean capable of being dissolved. • Liquids that are not soluble in each other are immiscible; liquids that are soluble in each other are miscible. • A concentrated solution has a large amount of solute as compared to solvent; a dilute solution has a small amount of solute as compared to solvent.

  5. Amount of solute compared to amount of solvent in a solution • Unsaturated: a solution that contains less than the maximum amount of dissolved solute • Saturated: a solution that contains the maximum amount of dissolved solute • Supersaturated: a solution that contains more than the maximum amount of dissolved solute under same conditions; not stable; will crystallize with single crystal

  6. Solutions, Colloids, Suspensions

  7. What dissolves in what? • The general rule of thumb for deciding if two substances will dissolve in each other is “Like dissolves like.” • “Like” refers to substances with similar particle size and, more importantly, similar forces (polarity).

  8. “Like Dissolves Like” • Nonpolar solutes  nonpolar solvents • Example: I2 dissolves in CCl4 • Polar solutes  polar solvents • Example: NH3 dissolves in H2O • But what about ionic solutes? There are no ionic solvents because ionic compounds are solids at room temp

  9. “Like Dissolves Like” (continued) • Since ionic compounds have total charges, they will dissolve in polar solvents that have partial charges • Ionic solutes  polar solvents • Example: NaCl in H2O

  10. Alcohols • Methanol (methyl alcohol) CH3OH • Ethanol (ethyl alcohol) CH3CH2OH or C2H5OH • Propanol (propyl alcohol) CH3CH2CH2OH or C3H7OH

  11. Solubility of Alcohols • Alcohols have a polar end (where –OH is) and a nonpolar end (where C/H chain is) • Alcohols can therefore dissolve both polar and nonpolar substances • Alcohols CANNOT dissolve ionic solutes

  12. Factors Affecting the Rate of Dissolving • Surface Area • Increasing surface area of solute increases rate of dissolving • Ex: cube of sugar vs granulated sugar • Agitation • Stirring or shaking solution increases rate of dissolving • Ex: dissolving sugar without stirring vs stirring • Heat • Heating solid solute increases its rate of dissolving into a liquid solvent • Ex: dissolving sugar in hot vs cold tea

  13. Factors Affecting Solubility • Type of solute and solvent • “Like dissolves Like” • Pressure • Only has effect on gases dissolved in liquids • Ex: colas bottle under pressure to have more fizz • Temperature • Solubility increases as temperature increases for solids dissolved in liquids • Ex: hot tea dissolves more sugar than cold tea • Solubility decreases as temperature increases for gases dissolved in liquids* • Ex: hot cola is flat (has less dissolved CO2) compared to a colder cola (has more dissolved CO2)

  14. Electrolytes vs Nonelectrolytes • Electrolyte – compound that conducts electricity in aqueous solutions or in its molten state due to the formation of ions • Examples on next two slides • Nonelectrolyte - Does not separate into ions in its molten state or aqueous state; does not conduct • Ex. Large Organic Molecules and other covalent compounds • C6H12O6, C12H22O11, CCl4

  15. Strong Electrolytes • 100% dissociation in water • Separates into ions; 100% ionized • Types of strong electrolytes • Strong, non-organic acids (start with H) • Ex. HI, HBr, HCl, H2SO4, HNO3, HClO4 • Strong Group 1 and 2 bases (bases are ionic compounds with a metal and the hydroxide ion (OH-)) • Ex. NaOH, Ca(OH)2, KOH, Ba(OH)2 • Soluble salts (Ionic compounds that dissolve in water); Remember, ionic compounds are metal and non-metal or compounds with polyatomic ions • Ex: NaF, KBr, FeCl3, NH4NO3

  16. Weak Electrolytes • Do not dissociate completely • Do not separate into ions 100%; not fully ionized • Types of weak electrolytes • Organic acids (start with H and contain carbon) • Ex. HC2H3O2 (acetic acid) • Bases with metals not in group 1 or 2 • Ex. Fe(OH)2, Al(OH)3

  17. Colligative Properties • Properties which depend upon the number of solute particles in solution, but are independent of the nature of the solute particles • 1) Vapor Pressure Lowering • 2) Freezing Point Depression • 3) Boiling Point Elevation

  18. Vapor Pressure Lowering • Vapor pressure is a measure of the tendency of molecules to escape from the surface of a liquid or solid • Vapor pressure is decreased proportionally to the number of solute particles in a solution

  19. Freezing Point Depression • When a substance freezes, the particles of the solid take on an orderly pattern; the presence of the solute particles disrupts this pattern. • The magnitude of freezing point depression is proportional to the number of solute particles in solution

  20. Boiling Point Elevation • When a substance boils, the particles of the liquid must attain enough energy to overcome intermolecular forces and escape into the gas form; the presence of solute ions makes it harder for these molecules to escape. • The magnitude of boiling point elevation is proportional to the number of solute particles in solution.

  21. Mathematically Expressing Concentration • Molarity (M) = moles solute L solution • molality (m) = moles solute kg solvent • Mass % = grams solute x 100% grams solution

  22. Practice Problems • What is the molarity of a solution containing 22.3 g of SCl6 dissolved in CCl4 to make 4.50 L of solution? • How much water should be added to 5.00 g KCl to prepare a 0.500m solution? • How many grams of solute are in 0.750 kg of a 65.0% aqueous solution of NaBrO3?

  23. Molarity (M) = moles solute L solution solute = SCl6 solvent = CCl4 22.3 g SCl6 x 1 mol SCl6 = 0.0910 mol SCl6 (solute) 245 g SCl6 There are 4.50 L total of solution M = 0.0910 mol = 0.0202 M SCl6 in CCl4 4.50 L You have 0.0202 M (molar) solution of SCl6 dissolved in CCl4.

  24. molality (m) = moles solute kg solvent solute = KCl solvent = H2O 5.00 g KCl x 1 mol KCl = 0.0671 mol KCl (solute) 74.5 g KCl The solution is 0.500m KCl (aq) 0.500 m = 0.0671 mol x = 0.134 kg H2O (solvent) x You have 0.0671 mol KCl solute dissolved in 0.134 kg H2O to make a 0.500m aqueous solution.

  25. mass % = grams solute x 100% grams solution solute = NaBrO3 solvent = H2O 0.750 kg solution x 1000 g = 750. g total solution 1 kg The solution is 65.0% NaBrO3(aq) 65.0% = x x = 488 g NaBrO3 (solute) 750. g You have 488 g NaBrO3 solute dissolved in H2O solvent to make a total of 750. g of a 65.0% aqueous solution.

  26. Dilution • Used for calculating how much concentrated acid should be used to make a more dilute acid solution • M1V1 = M2V2 concentrated diluted • mol (L) = mol (L) L L mol = mol

More Related