chapter 16: solutions concentration formulas freezing pt. depression boiling pt. elevation ch. 16...
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Chapter 16: Solutions
Concentration formulas
Freezing pt. depression
Boiling pt. elevation
Ch. 16
Making a solution
Concentration formulas
_____________ __________
Equation M = mole of solute . Liter of solution
m = mole of solute . kilogram of solvent
Effects Depends on temp. Does not depend on temp.
How do you make a solution?
• _________: process of surrounding solute particles with solvent particles to form a solution
• Heat of solution: overall energy change that occurs during the solution formation process
Speed of dissolving• Solution formation depends on how much
solute will dissolve in solvent.
Affect on dissolving
1__________________
2 __________
3 __________
Stir/agitate Solute dissolves faster
Increase temp Solute dissolves faster
Increase surface area Solute dissolves faster
Su
rfac
e ar
ea
Solubility – amount of solute that dissolves in solvent at a given _____________________________
Varying solubility of solution
1 _________ solution
2 ___________ Solution
3___________
_____ solution
Less solute than saturated solution
Contains maximum amount of solute at given temp and pressure
Contains more solute than it can theoretically hold at given temp. and pressure
Factors affecting solubility
Simulation: Solubility and temp
Factors affecting solubility
1Temper-
ature
• Increase temp
• __________solubility of solids
• Allows supersaturated soln. to be made
• _________ solubility of gases
• Crystallization of supersaturated soln. initiated by • ____________ • If container is scratched
Factors affecting solubility
Factors affecting solubility
2 Pressure
• Negligible for solubility of L and S
• Increase pressure gas increase solubility gas
• _______________
Section 2 Concentrations of Solutions
Objective:
Using Molarity (M)
1. Mass of solute in grams
2. Amount of solute in ____
3. Volume of solute in __
4. Molar concentration, __
Change to moles!!
1. What is the molarity of a solution prepared by dissolving 37.94 g of potassium hydroxide in some water and then diluting the solution to a volume of 500.0 mL?
Given:
Unknown:
Don’t forget to
use moles!
2. Determine the molarity of a solution prepared by dissolving 141.6 g of citric acid, C3H5O(COOH)3 in water and then diluting the resulting solution to 3500.0 mL.
Given:
Unknown:
3. What is the molarity of a salt solution made by dissolving 280.0 mg of NaCl in 2.00 mL of water?
Given:
Unknown:
mg… tricky?How do you get grams?
Here’s a hint: 1g = 1000 mg
4. What is the molarity of a solution that contains 390.0 g of acetic acid, HC2H3O2, dissolved in enough acetone to make 1000.0 mL of solution?
Given:
Unknown:
5. An analytical chemist wants to make 750.0 mL of a 6.00 M solution of sodium hydroxide. What mass of NaOH will the chemist need to make this solution?
Given:
Unknown:
6. What mass of glucose, C6H12O6 would be required to prepare 5.000x103 L of a 0.215 M solution?
Given:
Unknown:
Can you figure this
out?
7. A solution has a volume of 2.0 L and contains 36.0 g of glucose (C6H12O6). If the molar mass of glucose is 180 g/mol. What is the molarity of the solution?
Given:
Unknown:
8. A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is its molarity?
This is
CAKE!
Given:
Unknown:
Making Dilutions
• M1 V1 = M2 V2
•Question If you have 6M HCl acid, you want 500ml of 2M HCl acid, How can you prepare this?
Section 3: Colligative properties
• Property that depends on amount of solute in solution, and not on identity of solution.
Freezing point (FP)• Solute disrupts formation of orderly pattern; as a
result, more kinetic energy must be withdrawn from a solution to cause solidification.
* Solution that contains a solute has a ____________ than the pure solvent
Boiling point (BP)
• Since adding a solute to a solvent decreases VP, additional kinetic energy must be added to raise VP and initiate boiling.
* Solution that contains a solute has __________ than the pure solvent
Factors affecting Colligative Properties
1. Increase amt. of solute, increase magnitude…
a. VP lowering
b. FP depression
~1 mol solute lowers FP by 1.86°C
c. BP elevation
~ 1 mole solute increases BP by 0.512°C
2. Solutes that dissociate have greater effects than nondissociating (nonpolar) solutes
Factors affecting Colligative Properties
3 particles 6 particles 9 particles
Affect colligative property least
Affect colligative property most
Calculations with Colligative properties
• Freezing pt. depression (FP dep) – difference in temperature between FP of
solution and FP of pure solvent
ΔTf = (Kf)(m)
FP dep. example problems
FP dep example 1: What is the freezing point depression (ΔTf) of a 0.100 m solution made with water?
ΔTf = (Kf)(m)
FP dep. Example 2: A solution made with ethanol is made to lower the freezing point by 6.10˚C. What is the molality of the solution?
ΔTf = (Kf)(m)
Calculations with Colligative properties
• Boiling point elevation (BP elev.)– difference in temp between BP of a solution
and BP of pure solvent
ΔTb = (Kb)(m)
BP dep. example problems
BP elev. Example 1: What molality of NaCl solution would have to be used raise the boiling point of water by 2.00˚C?
ΔTb = (Kb)(m)
BP elev. Example 2: Determine BP elevation (ΔTb) of a 0.857 m CaCl2 solution?
ΔTb = (Kb)(m)