C h a p t e r 11C h a p t e r 11

Solutions and Their PropertiesSolutions and Their Properties

Kinds of Solutions 01Kinds of Solutions 01

Kind of Solution Example

Gas in gas Air (O2, N2, Ar …)

Gas in liquid Carbonated water

Gas in solid H2 in palladium metal

Liquid in liquid Gasoline (mixture)

Liquid in solid Dental amalgam(mercury in silver)

Solid in liquid Seawater (NaCl)

Solid in solid Metal alloys

Solute and solvent 02Solute and solvent 02

For Gas or solid dissolved in liquid:

SOLUTE - dissolved substance

SOLVENT - liquid

Liquids-liquids (minor component is solute)

Will a solution form? 03Will a solution form? 03

“LIKE DISSOLVES LIKE”

NaCl in water 04NaCl in water 04

Free-energy Change 05Free-energy Change 05

-∆G spontaneous substance dissolves

+∆G nonspontaneous substance does not dissolve

∆G = ∆H - T ∆S

∆Hsoln and ∆Ssoln

Entropy of Solution (∆Ssoln) 06Entropy of Solution (∆Ssoln) 06

∆Ssoln usually positive

Enthalpy of Solution (∆Hsoln) 07Enthalpy of Solution (∆Hsoln) 07

Solvent - Solvent: Energy is required (+ ∆H) to overcome forces between solvent molecules

Solute - Solute: Energy is required (+ ∆H) to overcome intermolecular forces holding solute particles together

Solvent - Solute: Energy is released (- ∆H) when solute particles are solvated (surrounded by solvent) greater for small cations increases with charge

Enthalpy of Solution (∆Hsoln) 08Enthalpy of Solution (∆Hsoln) 08

• Exothermic ∆Hsoln:

• Favorable process

• Hot packs - CaCl2(s)

Enthalpy of Solution (∆Hsoln) 09Enthalpy of Solution (∆Hsoln) 09

• Endothermic ∆Hsoln:

• Unfavorable process

• Cold packs - NH4NO3(s)

Examples 11Examples 11

1. Predict the relative solubilities in the following cases:

(a) Br2 in benzene (C6H6) and in water,

(b) KCl in carbon tetrachloride and in liquid ammonia,

(c) urea (NH2)2CO in carbon disulfide and in water.

2. Is iodine (I2) more soluble in water or in carbon disulfide (CS2)?

• Concentration: The amount of solute present in a given amount of solution.

1. Molarity (M)

2. Molality (m)

3. Mole fraction (X)

4. Mass Percent

Concentration Units 12Concentration Units 12

Concentration Units - important! 13Concentration Units - important! 13

• Molarity (M):

• Molality (m):

• Mole Fraction (X):moles of number Total

Aof MolesAX

SOLUTION of Literssolute of Moles

Molarity

SOLVENT of Kilogramssolute of Moles

=Molality

• Percent by Mass (weight percent): The ratio of the mass of a solute to the mass of a solution, multiplied by 100%.

% bymassof solute =

mass of solute

mass of solution 100%

mass of solution =mass of solute +mass of solvent

Concentration Units 14Concentration Units 14

Concentration Units 15Concentration Units 15

• Parts per Million:

• Parts per million (ppm) =

= % mass x 104

• One ppm gives 1 gram of solute per 1,000,000 g or one mg per kg of solution. For dilute aqueous solutions this is about 1 mg per liter of solution.

610xsolutionofmassTotal

componentofMass

Example 16Example 16

• A sample of 0.892 g of potassium chloride (KCl) is

dissolved in 54.6 g of water. What is the percent by

mass of KCl in this solution?

Example 17Example 17

An aqueous solution is 5.50% H2SO4. How many

moles of sulfuric acid (MM = 98.08 g/mol) are

dissolved in 250.0 g of the solution?

Example 18Example 18

• Molality from Mass: Calculate the molality of a

sulfuric acid solution containing 24.4 g of sulfuric

acid in 198 g of water. The molar mass of sulfuric

acid is 98.08 g.

Example 19Example 19

• Molality from Molarity: Calculate the molality of a

5.86 M ethanol (C2H5OH) solution whose density is

0.927 g/ml.

Solution Formation20Solution Formation20

Solute + solvent Solution

• Saturated - equilibrium (equal number of ions going into

solution as returning from solution to the crystals)

• Supersaturated - greater than equilibrium amount of solute

Solution Formation21Solution Formation21

• Solubility: A measure of how much solute will dissolve in a

solvent at a specific temperature (saturated solution)

• Miscible: Two (or more) liquids that are completely soluble

in each other in all proportions.

• Solvation: The process in which an ion or a molecule is

surrounded by solvent molecules arranged in a specific

manner.