Ch 13 Solutions Flashcards
Air is a solution, what is the solvent and the major solute?
Solvent is nitrogen
Majority solute is oxygen
3 types o f Solutions?
1) Gas - Formed by gas/gas
2) Solid - Formed by solid/solid
3) Liquid - Formed by liquid/gas, liquid/solid, or liquid/liquid
True or False? Gases are always soluble in each other?
True
Define Miscible
When two substances are soluble in each other in all proportions
What is the solubility of NaCl in 100g of water?
36g at 25 deg Celsius
40g at 100 deg Celsius
What is the “Chemists Rule of Thumb”?
Like dissolves like - Polar molecules and ionic compounds will dissolve in polar solvents. Non polar molecules will dissolve in non polar solvents.
Textbook examples of exothermic and endothermic reactions?
1) Exothermic - When NaOH is dissolved in water, heat is released and the container gets hot.
2) Endothermic - When NH4NO3 dissolves in water, heat is absorbed from the surroundings and the container gets cold.
4 common textbook Polar Solvents?
1) Water (H2O)
2) Acetone (CH3COCH3)
3) Methanol (CH3OH)
4) Ethanol (CH3CH2OH)
4 Common textbook Non-Polar Solvents?
1) Hexane (C6H14)
2) Diethyl Ether (CH3CH2OCH2CH3)
3) Toluene (C7H8)
4) Carbon Tetrachloride (CCl4)
Define Enthalpy
The sum of the internal energy of a system and the product of its pressure and volume; the amount of energy associated with the breaking and forming of bonds in a chemical reaction.
Define Enthalpy (heat) of Reaction
The Enthalpy change for a chemical reaction
🔺Hsoln = 🔺Hsolute+🔺Hsolvent + Hmix
What is the Heat of Hydration? 🔺Hhydration
The combination of 🔺Hsolvent and 🔺mix.
If |🔺Hsolute | < |🔺H hydration| then then the reaction is ______?
The reaction is negative and therefore exothermic.
If |🔺Hsolute | > |🔺H hydration| then then the reaction is ______?
The reaction is positive and therefore endothermic.
If |🔺Hsolute | = |🔺H hydration| then then the reaction is ______?
The reaction is equal therefore neither exothermic nor endothermic.
What is the opposite of dissolving? What are it’s practical use?
Recrystallization - it’s a good way of purifying substances.
Purification involves dissolving a solid in a hot solvent until the solution is saturated and as the solution SLOWLY cools, the solid crystallizes out, leaving the impurities behind.
What is the significance of the Solubility Curve of Solids?
It’s a graph that shows that for most Solids, the solubility of the solid increases as the temperature increases.
What is one exception to the Solubility Curve of Solids?
Cesium Sulfate Ce2(SO4)3
It’s solubility decreases as the temperature increases.
Define Saturated, Unsaturated and Supersaturated?
1) Saturated - When a solution has the solute and solvent in dynamic equilibrium; if you add more solute, it will not dissolve.
2) Unsaturated - A solution that has less solute than saturation; more solute will dissolve at this temp.
3) Supersaturated - A solution that has more solute than saturation.
How can a solvent hold more solute beyond dynamic equilibrium? aka supersaturation?
Saluting can be made saturated at no-room conditions and then allowed to come to room conditions slowly. For some solutes, instead of coming out of solution when the conditions change, they get stuck between the solvent molecules and the solution becomes supersaturated.
Supersaturated solutions are unstable and lose all the solute above saturation when disturbed.
i.e. shaking a carbonated beverage
Give and example of a Supersaturated Solution and it’s practical use?
Sodium Acetate NaC2H3O2 - used for heating packs. Can hold a Supersaturated state for a long time if not disturbed/cracked.
How does the temperature of solvent affect the solubility of gases?
For ALL gases, the solubility of the gas decreases as the temperature increases (the opposite of Solids).
How does the solubility of gasses in water compare to ionic and polar Covalent Solids’ solubility in water?
Gases generally have lower solubility in water than ionic or polar Covalent Solids because most are non polar molecules.
Explain Henry’s Law
Henry’s Law (Sgas = kH Pgas) - States that the solubility of a gas (Sgas) is directly proportional to its pressure (Pgas).
What are the Henry’s Law Constants for the following gases in water at room temperature (25 degrees celsius): O2 N2 CO2 NH3 He
1) O2 = 1.3 x 10 ^ -3
2) N2 = 6.1 x 10 ^ -4
3) CO2 = 3.4 x 10 -2
4) NH3 = 5.8 x 10 ^ 1
5) He = 3.7 x 10 ^ -4
Why is Henry’s Law Constant for Ammonia (NH3) so much larger than most other gases?
Because it is polar and will dissolve better in water (also polar) than most other gases that aren’t.
Define Concentration
Amount of solute in a given solution
How does the calculation for molality differ than the rest of the concentration calculations?
Molality is calculated using solute/solvent, whereas most other concentration calculations uses solute/solution. Where solution = solute + solvent.
How do you calculate Mole Percent?
Mole Percent = Mole Fraction x 100
How do you calculate percent by mass?
Solute/(Solute+Solvent)
Define Colligative Properties?
Properties whose values depend only on the number of solute particles and not the on what they are.
Value of the the property depends on the concentration of the solution.
What are the four Colligative Properties discussed in the textbook?
1) Lower Vapor Pressure
2) Lower Freezing Point
3) Higher Boiling Point
4) Osmotic Pressure
Describe Raoult’s Law?
The vapor pressure of a solution = the mole fraction of the solvent times the vapor pressure of the solvent at the same temperature.
Describe Vapor Pressure Lowering
The difference between the vapor pressure of the the pure solvent and the vapor pressure of the solvent in solution.
How do you calculate Kelvin?
Kelvin = Degrees In Celsius + 273
How do you convert from atm to torr(mmhg)?
1 atm = 760 torr(mmhg)
What is the value of R that represents the ideal gas constant of (atm-L)/(mol-K)?
R = 0.08206
Examples of isotonic solutions?
5% glucose
0.9% NaCl
What is crenation?
When RBCs shrink and shrivel up. Usually caused by hypertonic fluid outside the RBC that cause all the water to leave the cell via osmosis.
Describe the molecular make-up is soap?
Soap is a fatty acid that forms a colloid with a hydrophilic/ionic head and a hydrophobic/nonpolar tail.
What are the 5 types of Colloidal Dispersions?
1) Aerosol - Fog (water droplets in air)
2) Solid Aerosol - Smoke (ash in air)
3) Foam - Whipped Cream (air bubbles in butter fat)
4) Emulsion - Milk (milk fat globules in water)
5) Solid Emulsion - Opal (water in Silica glass)
Describe Miscelle Formation?
I.E. when soap forms a colloid, the head attract water molecules and the tails turn away forming a “bubble like structure”.
How do you calculate Freezing Point Depression and Boiling Point Elevation?
FPD = molality x Kf
BPE = molality x Kb