1. Solutions Regents Topic 7
Mr. Danahy
Chemistry
Nanuet HS

2. Solution vs. Suspension
Solution – homogeneous mixture
dissolving = physical change
(not a chemical change)
Dissolved particles (atoms, ions or molecules) are extremely small and solutions cannot be separated by filtering.
Suspension – heterogeneous mixture where some particles settle out upon standing ex. muddy water (clay & silt)

3. Tyndall Effect
Light beam is passed through a liquid containing particles in suspension; these particles scatters the light rays. The path of the light rays through the liquid becomes visible in a suspension, having the appearance of a bright cone in the liquid.
Ex. Fog – suspended water droplets
Tyndall Effect – car headlights in fog
- spotlight in smoke or dust

4. John Tyndall - Irish Physicist c. 1875
Large particles in suspension scatter the light rays. Path of the light rays in suspension are visible.

5. Tyndall Effect
Small particles (ions, molecules) in solution do not scatter the light rays. Path of the light rays in solution are not visible.
Suspension Solution
                           
Light
Beam

6. Solutions can be dilute (weak) or more concentrated.
Molarity (M) = expression of Concentration
M = # moles of solute
Liters of Solution
If 2.0 moles are dissolved in 4.0 Liters…
Molarity = moles / 4.0 L = M

7. Making Molar Solutions
Na 1x23 = 23g
Cl 1x35 = 35g
1 mole = 58 g
Fill to
Line

8. Calculate Molarity: Given 450 g NaCl (GFM = 58g) in 3.0 Liter.
M = # moles of solute
Liters of Solution
1) Find # moles (for numerator). Convert grams to moles using GFM.
2) Solve for Molarity.
M =

10. Aqueous Solutions
Solution - a homogenous mixture mixed molecule by molecule.
Solvent - the “stuff” that does the dissolving; larger amount than solute.
Solute - the “stuff” that is dissolved.
Exist in all phases – most common solid (solute) in liquid (solvent).
Aqueous solution (aq) - a solution with water as the solvent.

11. Solutions

12. Polar Water Molecules with Hydrogen Bonds = surface tension.
One water molecule H-bonds to another.
Other H-bonds to water molecules all around.

14. Dissolution & Hydration Water is a Polar Molecule

15. Hydration of Ions & Orientation of Polar Water Molecule

16. Factors Affecting Rate of Solution (Dissolving)
(Rate = how much over time)
Amount of Solute and Solvent
closer to max. limit = slower rate
Temperature – higher temp. = faster
Stirring – faster with stirring
Particle Size – smaller = faster

17. Factors Affecting Solubility (max. amount dissolved)
Nature of Solute and Solvent (“Like dissolves Like”) e.g., Polar solvents dissolve polar solutes.
Temperature
Solids - more hi. Temp.
Gases - less hi. Temp.
Pressure
Gases more hi. Pres.

18. “Like Dissolves Like” Polar solvents dissolve polar & ionic solutes.
Water (polar) dissolves ionic solids and polar covalent solids. Salts (NaCl, KCl) are ionic & form aqueous solutions.
Non-polar dissolves non-polar.
Oil (non-polar) and water (polar) don’t mix = immiscible.
Alcohols – dissolve polar & non-polar solutes; but not ionic solutes.
Tinctures – alcohol is solvent.

19. Solutions

20. Solubility Curves… show max. limit of solute dissolved for a given temp. and vol. of water. Supersaturated = above line Saturated = on the line Unsaturated = below; under the line
Temp.

21. Solubility Curves max. amount dissolved in 100g = 100mL of water
Supersaturated = above line
Saturated = on the line
Unsaturated = below; under the line

22. 1) How much KNO3 will dissolve in 100mL @ 50oC?
3) If 70g of HCl is 50oC in 100g H2O, is this Supersat., Sat. or Unsat.?

23. Solutions of Ionic Compounds conduct electricity = Electrolytes
Electrolytes – ions (charged particles) in solution.
NiCl2(aq) + KMnO4(aq)

24. Electrolytes - to conduct electricity in Liquid Phase, mobile (dissolved) ions are required
Greater number (#) ions in solution…
= greater electrical conductivity
= stronger electrolyte.

25. 3 Types of Electrolyte Compounds Salts (ionic compounds), acids(H+) & bases(OH-)
Solutions
bright
dim
dark
CH3COOH
C6H12O6
KCl
Salts = ionic = metal & non-metal K + (aq) & Cl - (aq)
Acetic = weak acid H + & CH3COO -
Covalent = no ions

26. Solutions Acids, Bases & Salts ; Release OH- (aq)
Salt (aq)  Metal +(aq) + Non-Metal – (aq)

27. Colligative Properties
Properties that depend on the
number of solute particles in solution;
not the nature of the particles
Best example:
Boiling Pt. Elevation
Freezing Pt. Depression
B.P.
100 C
F.P.
0 C

28. Electrolytes – form ions in solution KCl (aq)  1 K Cl –1 (1 mole) (2 moles particles) CaCl2 (aq)  1 Ca Cl –1 (1 mole) (3 moles of particles) Nonelectrolytes – exist as dissolved molecules (do not form ions) ex. Glucose C6H12O6 (aq) (1 mole)

29. Another Colligative Property Solute Effect on Vapor Pressure Vapor Pressure (V.P.) = pressure exerted by a vapor in equilibrium with its liquid (or solid) Volatile – substance has some V.P. Non-Volatile – V.P. = zero

30. Dissolved particles (solute = gray) occupy/prevent solvent particles from entering vapor phase.

31. Colligative Properties Summary
Greater # particles in solution = Greater effect for… - B.P. Elevation - F.P. Depression - Lower Vapor Press.

32. Which has the greater # particles … 1) NaCl (aq)
Which has the greater # particles … 1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq) Hint: Write a balanced dissociation reaction ___ NaCl (s)  ___ Na +1 (aq) + ___ Cl –1 (aq) Coefficients = # moles = # particles (aq)

33. Which has the greater # particles … 1) NaCl (aq)
Which has the greater # particles … 1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq) Hint: Write a balanced dissociation reaction ___ NaCl (s)  ___ Na ___ Cl – ___ CaCO3 (s)  ___ Ca ___ CO3 – ___ KCl (s)  ___ K ___ Cl –1 ___ Fe2O3 (s)  ___ Fe ___ O3 –2

34. Which has the greater # particles … 1) NaCl (aq). 2) CaCO3 (aq)
Which has the greater # particles … 1) NaCl (aq) 2) CaCO3 (aq) Total # Moles of 3) KCl (aq) 4) Fe2O3 (aq) Particles; Ions _1_ NaCl (s)  1 Na +1(aq) + 1 Cl –1(aq) _1_ CaCO3 (s)  1 Ca +2 (aq) + 1 CO3 –2 (aq) _1_ KCl (s)  1 K +1(aq) + 1 Cl –1(aq) _1_ Fe2O3 (s)  2 Fe +2 (aq) + 3 O3 –2 (aq) 5

35. Which has the greater Boiling Point (BP), lower Freezing Point (FP) and lower Vapor Pressure? 1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq) Because…_________________________________ _________________________________________

36. Which has the greater Boiling Point (BP), lower Freezing Point (FP) and lower Vapor Pressure? 1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq) Because… greatest # moles of particles are formed in solution when it dissolves. Fe2O3 (aq)  2 Fe +2 (aq) + 3 O3 –2 (aq) 5 moles

37. Vaporization vs. Condensation (opposing phase changes)
Liquid to Gas (evap.)
Open Container
Liquid evaporates completely = unlimited vaporiz.
No significant condensation.
Evap.

38. Physical Equilibrium Closed Container
Rate of Evap. = Rate of Condensat.
Dynamic Equilibrium between the 2 phases; exchange occurs in both directions equally (no net change).
Water level remains unchanged (no net change).

39. Physical Equilibrium of Saturated Solution
Rate of Precipitation = Rate of Dissolving
(equal opposing rates)
Sat.
Dissolved Particles
Solid = Precipitate

40. What kind of ratio does. “percent” mean
What kind of ratio does “percent” mean? For example, if a compound consists of 35% oxygen by mass, what does 35% represent (as a ratio)?

41. 1) What kind of ratio does “percent” mean?
35 % = 35
100
This is a ratio … X out of 100.

42. Percent Composition by Mass (Ref. Table T)
% Comp. = mass of part x mass of whole
Given 20.0 g of solute in g of solution; Calculate % Comp.

43. % Comp. = mass of part x 100 mass of whole
Given 20.0 g of solute in g of solution; Calculate % Comp.
% Comp. = 20 g solute x 100 = x 100
2000 g solution
% Comp. = 2 g solute x 100
200 g solution
% Comp. = 1 g solute x = %
100 g solution

44. Percent is ratio parts per hundred.
% = How many parts out of 100.
2 = = 20 %
Very small values such as 0.02 % are awkward. Use a smaller ratio, parts per million (ppm).
ppm = How many parts out of 1,000,000
= = .02 %
= = 200 ppm
1,000,000

45. Parts Per Million (ppm) (Table T) PPM is used for low concen.
ppm = grams of solute x 1,000, grams of solution
Given g of solute in g of solution; Calculate concen. in ppm.

46. Parts Per Million (ppm)
ppm = grams of solute x 1,000, grams of solution
Given g of solute in g of solution; Calculate concen. in ppm
ppm = g solute x 1,000, g solution
= ppm

47. Ref. Table F
Not-Soluble
Soluble
Soluble
Not-Soluble

48. Ref. J = Single Replacement
*** Elements higher on Ref. J replace lower elements.