Chapter 16: Solutions

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Chapter 16: Solutions Concentration formulas Freezing pt. depression Boiling pt. elevation Ch. 16 Making a solution

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Chapter 16: Solutions. Ch. 16. Concentration formulas. Making a solution. Freezing pt. depression. Boiling pt. elevation. Concentration formulas. How do you make a solution?. _________ : process of surrounding solute particles with solvent particles to form a solution - PowerPoint PPT Presentation

Transcript of Chapter 16: Solutions

Page 1: Chapter  16:   Solutions

Chapter 16: Solutions

Concentration formulas

Freezing pt. depression

Boiling pt. elevation

Ch. 16

Making a solution

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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.

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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

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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

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rfac

e ar

ea

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Solubility – amount of solute that dissolves in solvent at a given _____________________________

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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

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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

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Factors affecting solubility

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Factors affecting solubility

2 Pressure

• Negligible for solubility of L and S

• Increase pressure gas increase solubility gas

• _______________

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Section 2 Concentrations of Solutions

Objective:

Using Molarity (M)

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1. Mass of solute in grams

2. Amount of solute in ____

3. Volume of solute in __

4. Molar concentration, __

Change to moles!!

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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!

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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:

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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

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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:

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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:

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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?

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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:

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8. A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is its molarity?

This is

CAKE!

Given:

Unknown:

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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?

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Section 3: Colligative properties

• Property that depends on amount of solute in solution, and not on identity of solution.

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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

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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

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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

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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

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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

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FP dep example 1: What is the freezing point depression (ΔTf) of a 0.100 m solution made with water?

ΔTf = (Kf)(m)

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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)

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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

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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)

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BP elev. Example 2: Determine BP elevation (ΔTb) of a 0.857 m CaCl2 solution?

ΔTb = (Kb)(m)