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Chapter 12: Solutions Chem 1110

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1 Chapter 12: Solutions Chem 1110
Figures: Basic Chemistry 3rd Ed., Timberlake and Timberlake

2 Examples of Common Solutions
Solid Solutions: Brass (65% Cu, 35% Zn) White Gold (60% Au, 40% Pt) Liquid Solutions: Vinegar (95% water, 5% acetic acid) Solutions used in lab Gas Solutions: Air (78% N2, 20% O2, 1% Ar, 0.5% CO2, 0.5% H2O)

3 Solutions We need to define the important components in a solution:
Solvent: The most abundant substance in a solution Solute: Any substance dissolved in the solvent Aqueous Solution: a solution of any solute in water. Water is the solvent.

4 Solid Solutions Solid Solutions: An Alloy is a solid solution of metals: If one of the metals is mercury (Hg) we call this solution an amalgam Amalgams were commonly used in older dental work Brass (65% Cu, 35% Zn) White Gold (60% Au, 40% Pt)

5 Solutions Concentration is the amount of solute in a given volume of solution Concentrated Solution has a large amount of solute per volume Dilute Solution has a small amount of solute This is a Qualitative distinction, of course we will have to consider Quantitative values

6 Saturated Solutions We can add solute to a solvent until NO more solid will dissolve to form a Saturated Solution Saturation defines the solubility of the solute Solubility is the maximum amount of solute that can be dissolved in a given solvent

7 Solubility Solubility is based on: Pressure applied to the system
Temperature of the solution Nature of the solvent and solute interaction

8 Solubility increases as temperature increases:
Solubility in Water Solubility increases as temperature increases:

9 Supersaturated Solutions
If we heat a saturated solution to dissolve more solute, we can create a Supersaturated Solution: Supersaturated Solutions are: An Unstable State because there is too much solute for the amount of solvent Will precipitate out very easily Used to make hot packs for injuries

10 Solubility Temperature and Pressure affect solubility:
For solid or liquid solutes: Increasing T, increases solubility Supersaturated Solution Increasing P has NO effect on solubility For a gaseous solute: Increasing T, decreases solubility Increasing P, increases solubility Henry’s Law

11 Attractive Forces in Solutions
Interactions between solutes and solvents that: are similar in polarity will form a solution are not similar will not form a solution “Like dissolves like”

12 Water as a Polar Solute

13 Solubility “Like dissolves like”
Two liquids that dissolve into each other are said to be miscible If you consider Intermolecular Forces: “Like dissolves like” Ethanol and water are miscible Hexane and water are immiscible

14 Like Dissolves Like Solvents Solutes Water (polar) Ni(NO3)2
CH2Cl2(nonpolar) (polar) I2 (nonpolar)

15 Units of Concentration
We report the concentration of solutions in many different units: There are several important Career specific units to consider: Percent by Mass (m/m) Percent by Volume (v/v) Concentrations in chemistry are most often reported in Molarity (M)

16 Percent by Mass = mass of solute x 100%
Percent by Mass (m/m) is used most often in engineering or agricultural applications Commonly measured in grams Percent by Mass = mass of solute x 100% mass of solution 6.0 % (m/m): 6.0 g of solute dissolved in a total of 100 g of solution (6 g solute and 94 g solvent)

17 Percent by Mass Low fat milk has 1% (m/m) milkfat
This means that in this sample of milk there is… © Brooks/Cole, Cengage Learning. All rights reserved.

18 Percent by volume = volume of solute x 100%
Percent by Volume (v/v) is used most often when both solute and solvent are liquids or gases: Percent by volume = volume of solute x 100% volume of solution 17.0 % (v/v): 17.0 mL of solute dissolved in a total of 100 mL of solution (17 mL solute and 83 mL solvent)

19 Percent by Volume Rubbing alcohol is 70% (v/v) isopropanol in a solution with water This means that in the bottle there are… © Brooks/Cole, Cengage Learning. All rights reserved.

20 Molarity (M) = moles of solute
Molarity (M) is the unit of concentration most often used in chemistry labs: Molarity (M) = moles of solute 1 liter of solution A solution that has 1 mole of solute dissolved in a total of 1 liter of solution is said to be 1 molar (1 M) Molarity (M) = moles liter

21 Learning Check How many grams of CuSO4 ( amu) are needed to make exactly 500 mL of a 1.00 M solution?

22 Learning Check How many moles of CuSO4 are in 150 mL of the 1.00 M solution?

23 Dilution We decrease the concentration (or dilute) aqueous solutions by adding water The moles of solute STAYS THE SAME The volume of the solution changes Results in a change of molarity (M) Molarity decreases

24 Dilution In a dilution: water is added volume increases
concentration decreases

25 Dilution Initially: Molarity (M1) x volume (V1) = # moles solute After Dilution: New molarity (M2) x volume (V2) = # moles solute # moles solute = # moles solute M1V1 = M2V2 V2 = V1 + Vadded

26 Dilution What is the molarity of a the final solution after diluting 150 mL of a 1.0 M CuSO4 solution with 200 mL of water?

27 Molarity in a Chemical Equation
How many milliliters of a 3.00 M HCl solution are needed to react with 4.85 g of CaCO3? 2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)

28 Zn(s) + 2 HCl(aq) ZnCl2 (aq) + H2(g)
Learning Check How many liters of H2 gas at STP are produced when 6.25 g of Zn react with 20.0 mL of a 1.50 M HCl solution? Zn(s) + 2 HCl(aq) ZnCl2 (aq) + H2(g)

29 Colligative Properties
Homogeneous solutions may have different physical properties than the pure substances that they contain Properties of substances in a solution may be different: We will talk about adding nonvolatile solute leads to Increased melting point Increased boiling point Decreased vapor pressure

30 Colligative Properties
Colligative Properties are properties of solutions that depend on the number of particles dissolved in the solvent Colligative Properties do not depend on the identity of the particle: Ions Covalent Molecules It is the concentration of particles that matters, particle molarity

31 Colligative Properties
Dissolved Particles in a solution: 1 sugar molecule → 1 sugar molecule Total of 1 particle in solution 1 NaCl formula unit → 1 Na+ ion Cl- ion Total of 2 particles in solution (NH4)3PO4 →

32 Particle Molarity Dissolved Particles in a solution:
1 M sugar molecule → 1 M sugar molecule Total of 1 M particles in solution 1 M NaCl formula unit → 1 M Na M Cl- Total of 2 M particles in solution 1 M (NH4)3PO4 → 3 M NH M PO43- Total of 4 M particles in solution

33 Learning Check What is the molarity of particles in a solution of 125 g of MgCl2, a strong electrolyte, dissolved in L of water?

34 Colligative Properties
A large number of solute particles may cause interruptions or “get in the way” of the solution surface: Dissolved particles may disrupt intermolecular forces The pure substance is “diluted” by the solute Decrease solvent-solvent interactions on the surface

35 Colligative Properties
Solute particles (ionic or molecular) can: Interrupt the intermolecular forces holding the molecules of a solvent together Weaken the intermolecular forces of the solvent “Get in the way” on the surface of a solution and make it more difficult for molecules to escape

36 Colligative Properties
Colligative Properties may include: Boiling Point Elevation Freezing Point Depression Osmotic Pressure

37 Colligative Properties
Effect on Boiling Point… It is common to add salt to water when boiling, why? Adding a non-volatile solute may lower vapor pressure Ions interfere with solvent-solvent interactions on the surface Ions make it harder for water molecules to escape Fewer solvent (water) particles on the surface

38 Colligative Properties: Boiling Point Effects
Ions make it harder for water molecules to escape Fewer solvent (water) particles on the surface

39 Colligative Properties
Boiling Point Effects: A higher temperature is needed to get the vapor pressure to equal atmospheric pressure DECREASE the vapor pressure of the solution INCREASE the boiling point of the solution INCREASE number of particles for a larger effect Adding salt to water raise boiling temperature: 1 mole of particles raises boiling point by 0.52 °C Antifreeze in car engines raises boiling point in radiator

40 Colligative Properties
Effect on Freezing Point… Why do we add salt to roads in winter? Salt interferes with intermolecular forces holding the H2O molecules together Water molecules are not able to organize into ice crystals since solute is in the way A lower temperature is needed to reach the solid state The Freezing Point is DECREASED

41 Colligative Properties
Why do we add salt to roads in winter? Salt interferes with intermolecular forces holding the H2O molecules together Water FREEZES at a lower temperature Salt prevents roads from re-freezing but it DOES NOT melt the ice!! CaCl2 (Ice Melter®) melts ice and lowers the melting temperature even colder The oceans never freeze solid due to higher salt concentrations

42 Osmosis OSMOSIS: the transport of a solvent across a semi-permeable membrane We will limit our discussion to water as the solvent Water moves across the membrane to create an isotonic system

43 Example of Osmosis A semi-permeable membrane separates a 4% starch solution from a 10% starch solution. Starch is a colloid and cannot pass through the membrane, but water can. What happens? 10% starch 4% starch H2O Semi-permeable membrane

44 Example of Osmosis (continued)
The 10% starch solution is diluted by the flow of water out of the 4% solution, and its volume increases The 4% starch solution loses water, and its volume decreases Eventually, the water flow between the two becomes equal 7% starch H2O 7% starch H2O

45 Osmotic Pressure Water flows from less concentrated to more concentrated side of a semi-permeable membrane Movement of water molecules sets up a pressure differential Osmotic Pressure is the pressure required to make these two sides equal equilibrate

46 Hypotonic, Hypertonic, Isotonic Solutions
Maintaining appropriate solution conditions are very important in your body and chemistry Consider the possible negative effects…

47 Isotonic Fluid Consider, an isotonic solution such as blood:
Blood plasma (liquid) should have the same osmotic pressure as in your red blood cells: 5.0% (m/v) glucose 0.9% (m/v) NaCl

48 Red Blood Cell: Isotonic Solution
Dr. Stanley Flegler/Getty Images Composition of cell is similar to the isotonic solution it is in – no significant osmosis

49 Red Blood Cell in Hypotonic Solution Hemolysis
David H. Phillips/Photo Researchers Water flows into the cell to dilute the solution inside (from the hypotonic solution)

50 Red Blood Cell in Hypertonic Solution Crenation
David H. Phillips/Photo Researchers Water flows out of the cell to dilute the hypertonic solution outside

51 Colloidal Solution A homogeneous mixture, NOT a true solution
No solute or solvent Contains dispersed particles that are intermediate in size between those of a solution and those of an ordinary heterogeneous mixture So, have dissolved solids in solvent Fog Milk

52 Tyndall Effect Colloidal Solutions scatter light (Tyndall Effect):
True Solution: No Scattering Colloidal Solution: Light Scatters

53 Suspension Suspension: a heterogeneous mixture containing dispersed particles that are heavy enough to settle out under the influence of gravity: Muddy water Blood Fine precipitates

54 Suspension Colloidal Dispersion Homogeneous Groups of small particles or individual larger molecules Scatters light (Tyndall effect) Particles do not settle Particles cannot be filtered out Heterogeneous Very large particles, which are often visible Not transparent Particles settle rapidly Particles can be filtered out

55 Solutions, Colloids, and Suspensions

56 Dialysis Dialysis is similar to osmosis
Uses a semi-permeable membrane that allows the passage of solvent, dissolved ions, and small molecules, but blocks the passage of colloidal-sized particles and large molecules:

57 Removing Colloidal Impurities

58 Artificial Kidney Machine

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