SOLUTIONS

solution – a homogeneous mixture, may be:– solids– liquids– gases

solute – the substance that dissolves

solvent – the dissolving medium

H2O is the “universal solvent”

soluble – a substance that dissolves in a solvent

insoluble – a substance that does not dissolve in a solvent

solvation – the process of surrounding solute particles with solvent particles to form a solution

Solvation• When a solid solute is placed in a solvent, the

solvent particles completely surround the surface of the solid solute.

• If attractive forces between the solute particles and the solvent are greater than the attractive forces holding the the solute particles together, the solvent particles pull the solute particles apart and surround them.

+

-

--

-+

+

-+

+

NaCl

Na =

Cl =

H2O

H =

O =

+

-+--+ +

-+-

- + -

+-+

-

+

-+ +

-++

-+

+- +

+

+

-+

+

Process of Solvation

Water- Universal Solvent• Polar molecule

• Dipoles allow solvation of ions and polar molecules

Factors that Affect the Rate of Solvation

1.Agitate the solution (stirring)

2. increase the temperature of solvent

3. increase the surface area of the solute

SOLUBILITY – refers to the maximum amount of solute that will dissolve in a given amount of solvent (at a specified temperature and pressure)

saturated – a solution that contains the maximum amount of dissolved solute (for a given temp & pressure than a saturated solution)

unsaturated – a solution that contains less dissolved solute (for a given temp & pressure than a saturated solution)

Units of Solubility

g of solute

100 g water

read these units as:

“grams of solute per 100 grams of water”

Here are some for you to try.

What mass of solute will dissolve in 100mL of water at the following temperatures. Also determine which of the three substances is most soluble in water at 15°C.

1. KNO3at 70°C

2. NaCl at 100°C

3. NH4Cl at 90°C  

supersaturated – a solution that contains more dissolved solute than a saturated solution at the same temperature

- is above the solubility curve

solute will usually precipitate out of solution

Sodium Acetate Supersaturation

http://dwb4.unl.edu/Chemistry/DoChem/DoChem058.html