copyright©2000 by houghton mifflin company. all rights reserved. 1 chemistry properties of...

Copyright©2000 by Houghton Mifflin Company. All rights

reserved.

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Chemistry

Properties of Solutions


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What is one of the most important Substances on earth????????????

Water!!!!!!!!!!!!!!!!!!!!!

What is one of its most valuable properties?

Its ability to dissolve many different substances!!


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Solutions

. . . the components of a mixture are uniformly intermingled (the mixture is homogeneous).


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Solutions can be

• GasesEx. Air

• Solids

Ex. Brass

• LiquidsEx. Carbonated water


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Focus

is

the properties of liquid solutions,particularly those containing water.


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Water, The Common SolventAqueous Solutions

Water is the dissolving medium, or solvent.


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•Figure 4.1

The Water Molecule is

· Polar

·Bent


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Some Properties of Water Water is “bent” or V-shaped. The O-H bonds are covalent. Water is a polar molecule. Electrons are not equally shared. Unequal charge distribution.

O—H δ- δ+

Hydration occurs when salts dissolve in water.Polarity gives water ability to dissolve cpds.


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Polar Water Molecules Interact with the Positive and Negative Ions of a Salt


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SOLUTION COMPOSITION

• SOLUTE - SUBSTANCE BEING DISSOLVED

• SOLVENT – DISSOLVING MEDIUM

• IF SOLID IN A LIQUID, THEN LIQUID IS SOLVENT

• IF LIQUID IN LIQUID, THE LIQUID OF LARGER AMOUNT IS SOLVENT.


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SOLUTION

• HOMOGENEOUS MIXTURE

• Solvent – Dissolving medium

• Solute – Substance dissolved


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A Solute dissolves in water (or

other “solvent”)

changes phase (if different from the solvent)

is present in lesser amount (if the same phase as the solvent)


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A Solvent

retains its phase (if different from the solute)

is present in greater amount (if the same phase as the solute)

• Solution - Solution - homogeneous mixture

Solvent Solvent – dissolving medium

Solute Solute - substance being dissolved


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Factors Affecting how quickly solutions are formed

(Rate of solution formation)

• Stirring or agitation

• Particle size (grinding/crushing)

• Temperature


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Solubility

• The amt of a solute that dissolves in a given amt of solvent at a specified temperature.


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Solubility

• Saturated solution-- Contains the max. amt of solute for a given amt of solvent at constant T & P (g solute/ 100 g solvent)

• Unsaturated solution-- Contains less than the max. amt of solute for a given amt of solvent at constant T & P


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Solubility

• Supersaturated solution --Contains less than the max. amt of solute for a given amt of solvent at constant T & P


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Factors Affecting Solubility

• STRUCTURE EFFECTS

-- “LIKE DISSOLVES LIKE”

-- SOLUBILITY IS FAVORED IF SOLUTE AND SOLVENT HAVE SIMILAR POLARITIES.

-- POLARITY DETERMINED BY MOLECULAR STRUCTURE


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Solubility

• “LIKE DISSOLVES LIKE”

• Polar substances dissolve polar substances

• Nonpolar substances dissolve nonpolar substances


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PRESSURE EFFECTS

• PRESSURE HAS

--- LITTLE EFFECT ON SOLUBILITY OF SOLIDS AND LIQUIDS

--- SIGNIFICANTLY INCREASES SOLUBILITY OF A GAS


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Figure 11.5

A Gaseous Solute


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Henry’s Law

P = kC

P = partial pressure of gaseous solute above the solution

C = concentration of dissolved gask = a constant

The amount of a gas dissolved in a solution is The amount of a gas dissolved in a solution is directly proportional to the pressure of the gas directly proportional to the pressure of the gas above the solution.above the solution.


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TEMPERATURE EFFECTS

• SOLUBILITY OF MOST SOLIDS IN WATER INCREASES WITH TEMPERATURE.

• SOLUBILITY OF SOME SOLIDS IN WATER DECREASE WITH TEMPERATURE.


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Figure 11.6

The Solubilities of Several Solids as a Function of Temperature


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SOLUBILITY OF GASES IN WATER

• DECREASES WITH INCREASING TEMPERATURE.


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Figure 11.7

The Solubilities of Several Gases inWater


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• The Composition of Solutions

Important to know the Amount of Chemicals present in a Solution.


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Solution Composition

1. Molarity (M) =

2. Mass (weight) percent =

3. Mole fraction (A) =

4. Molality (m) =

moles of soluteliters of solution

mass of solutemass of solution

100%

molestotal moles in solution

A

moles of solutekilograms of solvent


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Molarity

Molarity (M) = moles of solute per volume of solution in liters:

M

M

molaritymoles of soluteliters of solution

HClmoles of HCl

liters of solution3

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Molarity

• Concentration of a solution

solution of liters

solute of moles(M)Molarity

total combined volume

substance being dissolved

C. Molarity

2M HCl

L

molM

nsol' L 1

HCl mol 2HCl 2M

What does this mean?

C. Molarity Calculations

• How many grams of NaCl are required to make 0.500L of 0.25M NaCl?

0.500 L sol’n 0.25 mol NaCl

1 L sol’n

= 7.3 g NaCl

=.125 mol NaCl

58.44 g NaCl

1 mol NaCl

.125 mol NaCl

C. Molarity Calculations

• Find the molarity of a 250 mL solution containing 10.0 g of NaF.

10.0 g NaF 1 mol NaF

41.99 g NaF

L

molM .283 NaF

.25 L sol’n= 0.95 M

NaF

=.283 mol NaF

• Percent Composition by Mass

Mass of SoluteMass of Solution

x100

Percent by Mass

• How many moles of solute are contained in 343 grams of a 23% aqueous solution of MgCr2O7?

343g of solution 23%

100%

1 mol

240.3 g MgCr2O7

=0.329 mol of MgCr2O7

• Percent Composition by Volume

Volume of SoluteVolume of Solution

x100

B. Percent by Volume

• Determine the percent by volume of toluene (C6H5CH3) in a solution made by mixing 40.0 mL of toluene with 75.0 mL of benzene (C6H6).

40.0 mL toluene + 75.0 mL benzene= 115 mL total solution(40.0 mL toluene / 115 mL solution) 100 = 34.8%

toluene

Mole Fraction

Moles A

Total Moles= Mole Fraction, Χ

Molality

solvent ofkg

solute of moles(m)molality

mass of solvent only

1 kg water = 1 L waterkg 1

mol0.25 0.25m

D. Molality

• Find the molality of a solution containing 75 g of MgCl2 in 250 mL of water.

75 g MgCl2 1 mol MgCl2

95.21 g MgCl2

= 3.2m MgCl2

0.25 kg water

kg

molm

D. Molality

• How many grams of NaCl are req’d to make a 1.54m solution using 0.500 kg of water?

0.500 kg water 1.54 mol NaCl

1 kg water

= 45.0 g NaCl

58.44 g NaCl

1 mol NaCl

kg 1

mol1.54 1.54m


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Standard Solution

• Solution whose concentration is accurately known.


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Figure 4.10

Preparation of a Standard Solution


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Dilution

• Solutions are often prepared by diluting more concentrated solutions.


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Common Terms of Solution Concentration

Stock - routinely used solutions prepared in concentrated form.

Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl)

Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)


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“Solutions by Dilution”

• Moles of solute after dilution

EQUALS

Moles of solute before dilution

• M2 x V2 = M1 x V1

Dilution

• What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?

GIVEN:

M1 = 15.8M

V1 = ?

M2 = 6.0M

V2 = 250 mL

WORK:

M1 V1 = M2 V2

(15.8M) V1 = (6.0M)(250mL)

V1 = 95 mL of 15.8M HNO3


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Figure 4.11(a) A Measuring Pipet (b) A Volumetric (transfer) Pipet

copyright©2000 by houghton mifflin company. all rights reserved. 1 chemistry properties of...

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solvent slide

gas slide

gaseous solute slide

carbonated water slide

salt slide

amt of solute

nonpolar substances