Solutions & Solubility

ChemistryMrs. Stoops

General Chapter16Accelerated Chapter 13

Parts of a Solution

What is being

dissolved

What is DOING the dissolving

Miscible Immiscible

Miscible and Immiscible describe whether two liquids will mix with each other or not

Factors that Affect Solution Formation

Stirring Particle Size Temperature

Solubility - saturatedAbility to be dissolved

Solubility - Supersaturated

Highly unstable

Saturated solution that was heated and more solute was added. Then the solution was cooled slowly

Addition of one piece can cause crystals to form (shown above)

Factors affecting solubility

Pressure

Temperature

Gases only

The type of substance – solute and

solvent interaction

Solubility Graph

Amount that can

dissolve

Above the line

On the line

Below the line

There is extra

Completely

dissolves

More could dissolve

What is solubility of KNO3 at 50 C?

80 g per 100 mL H2OIf the temperature

changes from 90 C to 50 C, what happens to NH4Cl?20 g falls out of

solution

Units of Concentration

• Need to be more specific than “a lot” or “a little” • Describes how much solute is dissolved in a

solution• Examples include:

– Ppm– Ppb– Molarity– % by mass– % by volume– Molality– And others

Molarity

• Describes amount of solute dissolved in a specific amount of solution

• Units are molar (or molarity)• Abbreviated M• Can be whole numbers or decimals

solution of literssolute of moles

Molarity

Molarity Examples

• Determine the molarity of a solution made by dissolving 15 gKCl into 25 mL of water

KCl mol 0.20KCl 74gKCl 1mol

KCl 15g Part 1

Part 2

M 8.00.025L

KCl 0.20mol

Molarity Examples

• What mass of MgCl2 is needed to make a 250 mL solution that has a molarity of 0.15M?

0.250LMgCl moles ?

0.15M 2Part 1

0.0375 mol MgCl2

Part 2

22

22 MgCl 3.53g

MgCl 1molMgCl 94g

MgCl 0.0375mol

% by Mass

• Compares the amount of solute (or solvent) in a certain amount of solution

• By mass (so grams usually)

100solution of mass total

component of mass%mass

Example

• If the percent (mass/mass) for a solute is 4 % and the mass of the solution is 200 g, what is the mass of solute in the solution?

100solution of mass total

solute of massmass %

g 82000.04

% by Volume

• Same as % by mass except uses volume• Usually mL or L

100solution of volume total

component of volume%volume

Example

If the volume of solute is 6.0 mL and volume of solution is 300.0 mL, what is the solute’s percent by volume?

% 2.0 100mL 300.0

mL 6.0volume %