Chapter 6 2

Water

• Colorless, odorless, and tasteless• Density of ice < than density of liquid

water– Water expands when it freezes– Ice floats on water– Density of liquid water = 1.00 g/mL– Density of ice = 0.917 g/mL

Chapter 6 3

Water (cont.)

• Freezes at 0°C• Boils at 100°C at 1.00 atm pressure– Boiling point increases as atmospheric

pressure increases• Temperature stays constant during a

state change• Relatively large amounts of energy

needed to melt solid or boil liquid

Chapter 6 4

Water (cont.)

Chapter 6 5

Structures of the States of Matter

Chapter 6 6

Solutions

• Homogeneous mixture of two or more substances

• Solute – what is being dissolved• Solvent – what is doing the dissolving• Aqueous solutions – water is solvent

Chapter 6 7

Solubility

• Soluble: an appreciable quantity dissolves • Insoluble: very little, if any, quantity dissolves• Dilute solution: little solute in a lot of water• Concentrated solution: lots of solute in the

solvent

Chapter 6 8

Solutions (cont.)

Tro's Introductory Chemistry, Chapter 13 9

Will It Dissolve In Water?• ions are attracted to polar solvents– many ionic compounds dissolve in water

• polar molecules are attracted to polar solvents– table sugar, ethyl alcohol and glucose all dissolve well in

water• nonpolar molecules are attracted to nonpolar solvents– -carotene, (C40H56), is not water soluble; it dissolves in

fatty (nonpolar) tissues• many molecules have both polar and nonpolar

structures – whether they will dissolve in water depends on the kind, number and location of polar and nonpolar structural features in the molecule

Tro's Introductory Chemistry, Chapter 13 10

Salt Dissolving in Water

Tro's Introductory Chemistry, Chapter 13 11

Solvated Ions

When materials dissolve, the solvent molecules surround thesolvent particles due to the solvent’s attractions for the solute. The process is called solvation. Solvated ions are effectivelyisolated from each other.

Tro's Introductory Chemistry, Chapter 13 12

Solubility• there is usually a limit to the solubility of one

substance in another– gases are always soluble in each other– two liquids that are mutually soluble are said

to be miscible • alcohol and water are miscible• oil and water are immiscible

• the maximum amount of solute that can be dissolved in a given amount of solvent is called the solubility

Tro's Introductory Chemistry, Chapter 13 13

Why do we do that?• we spread salt on icy roads and

walkways to melt the ice• we add antifreeze to car

radiators to prevent the water from boiling or freezing– antifreeze is mainly ethylene glycol

• when we add solutes to water, it changes the freezing point and boiling point of the water

Tro's Introductory Chemistry, Chapter 13 14

Colligative Properties• the properties of the solution are different

from the properties of the solvent• any property of a solution whose value

depends only on the number of dissolved solute particles is called a colligative property– it does not depend on what the solute particle is

• the freezing point, boiling point and osmotic pressure of a solution are colligative properties

Tro's Introductory Chemistry, Chapter 13 15

Drinking Seawater

Because seawater hasa higher salt concentrationthan your cells, water flowsout of your cells into theseawater to try to decreaseits salt concentration.

The net result is that, insteadof quenching your thirst,you become dehydrated.

Tro's Introductory Chemistry, Chapter 13 16

Osmotic Pressure

Solvent flows through a semipermeable membrane to make thesolution concentration equal on both sides of the membrane. The pressure required to stop this process is the osmotic pressure.

Tro's Introductory Chemistry, Chapter 13 17

Hemolysis & Crenation

normal red bloodcell in an isotonic

solution

red blood cell inhypotonic solution – water flows into

the cell –eventually causing

the cell to burst

red blood cell inhypertonic solution – water flows out

of the cell –eventually causingthe cell to distort

and shrink

Chapter 6 18

Measurement of Solubility

• Molarity (M): amount of solute, in moles, per liter of solution

Chapter 6 19

Example 6.18

Calculate the molarity of a solution made by dissolving 3.50 mol of NaCl in enough water to produce 2.00 L of solution.

Exercise 6.18A

Calculate the molarity of a solution that has 0.0400 mol of NH3 in 5.75 L of solution.

Calculate the molarity of a solution made by dissolving 0.650 mol of H3PO4 in enough water to produce 775 mL of solution.

Chapter 6 20

Example 6.19

What is the molarity of a solution in which 333 g of potassium hydrogen carbonate is dissolved in enough water to make 10.0 L of solution?

Exercise 6.19

Calculate the molarity of each of the following solutions:

a. 18.0 mol of H2SO4 in 2.00 L of solution

b. 3.00 mol of KI in 2.39 L of solution

c. 0.206 mol of HF in 752 mL of solution. (HF is used for etching glass.)

Chapter 6 21

Example 6.20 How many grams of NaCl is required to prepare 0.500 L of typical over-the-counter saline solution (about 0.15 M NaCl)?

Exercise 6.20

How many grams of potassium hydroxide is required to prepare each of the following solutions?

a. 2.00 L of 6.00 M KOH

b. 100.0 mL of 1.00 M KOH