Chemistry - Unit 10 -Solutes/Solubility

FIRST TOPIC

Dissolving into Ions

Solute: The substance that is dissolved

Solvent: The substance that is doing the dissolving (typically water)

Solution: Homogenous mixture of solute and solvent

Saturated: A solution that contains the maximum amount of dissolved solute for a given amount of solvent

• You can see some undissolved solute at the bottom (heterogenous)

Unsaturated: A solution that contains less than the maximum amount of dissolved solute for a given amount of solvent

• You cannot see the solute, it is fully dissolved

Temperature and Solubility - Solid in Liquid

1. As temperature increases, the solubility increases

   1. Solvent molecules interact with solute more frequently to separate the ions (overcome IMFS)

2. As temperature decreases, the solubility decreases

   1. Solvent molecules interact with solute less frequently to separate the ions (overcome IMFs)

• DIRECT RELATIONSHIP, ONE INCREASES THE OTHER INCREASES AND VICE VERSA*

Temperature and Solubility - Gas in Liquid

1. As the temperature increases, the solubility of a gas decreases

   1. Gas particles move more, take up more space and escape the liquid

2. As the temperature decreases the solubility of a gas increases

   1. Gas particles move less, taking up less space, and stay dissolved in the liquid

• INDIRECT RELATIONSHIP, ONE INCREASES THE OTHER DECREASES AND VICE AND VERSA*

LESSON 2

Using Table G

Table G is titled as Solubility Curves at Standard Pressure. The x-axis title is Temperature and the y-axis is Solubility (g solute/100. g H2O). This chart shows us how much of each substance dissolves in 100g of water, emphasis on 100 grams, at different temperatures.

MAKE SURE TO CHANGE THE AMOUNT OF WATER TO 100G (EX: if its out of 200 multiply maximum solute by two)

NOTICE:

Gases lines decrease as temperature increases

Solid lines increase as temperature increases

LESSON 3

Crystallization: a crystal precipitate from a liquid

• in a saturated solution the rate at which a solid dissolves is equal to or greater than the rate at which is crystallizes

Supersaturated: More than the maximum amount of solute is dissolved in a solvent at a given temperature

• Solution needs to be heated up and then cooled down to make a supersaturated solution

LESSON 4

Increase gas solubility (to decrease, do the opposite)

1. Temperature decrease: increases gas solubility, particles move less and don’t escape

2. Pressure increase: Prevents gas particles from escaping container

Increase solid solubility

1. Temperature increase: increases solid solubility, more energy added to break apart bonds

2. PRESSURE HAS NO EFFECT ON THE SOLUBILITY OF SOLIDS BECAUSE THE SOLID LATTICE STRUCTURE CANNOT BE COMPRESSED

Rate of solubility: How fast something dissolves (no effect on how MUCH can dissolve)

1. STIRRING/MIXING: The more you physically mix a solution (increase particle interactions) the faster the solute dissolves

2. Particle Size/Surface Area: the smaller the particles, the greater amount of total surface area. More surface area = more interaction between solute and solvent particles and faster dissolving

3. Polarity: solute and solvent will only mix if they have similar polarity (polar and polar, non polar and non polar, like mixes with like)

LESSON 5

Concentration: the amount of substance (solute) in a given amount of solvent

1. Tells us the specific amount of solute in a solvent (quantitative)

2. Concentrated and dilute are not specific (qualitative) and just tells us GENERALLY if solutions have higher/lower concentrations

Molarity: a measure of concentration noted in the moles per liter followed by a M (ex: #M)

1. Moles solute/Liters solution M= m/L (moles per liter)

Parts Per Million - a measure of concentration, notated as PPM

1. “Per million” —> like percent but not by 100, by 1,000,000

2. Calculated as: mass of solute/mass of solvent x 1,000,000

LESSON 6

Colligative properties

1. When solute is added to a solvent particles of solute get in the way of the solvent molecules transitioning to the gas phase

   1. VAPOR PRESSURE DECREASES AS SOLVENT IS ADDED

2. Because transitioning to gas phase is now harder with lower vapor pressure (less molecules being able to escape due to pressure) the kinetic energy required to phase change to gas increases, increases KE required means higher boiling temp

   1. BOILING TEMPERATURE INCREASES AS SOLVENT IS ADDED

3. Solute interferes with the ability of solutions to form the solid lattice of crystal structure

   1. FREEZING POINT OF SOLUTION DECREASES AS SOLVENT IS ADDED

4. The more concentrated the solution, the larger the effect on the freezing point AND boiling point, again more energy is needed to be lost or added to phase change due to the annoying solvent particles being in the way

   1. MORE CONCENTRATED = BIGGER IMPACT (INCREASE IN BOILING, DECREASE IN FREEZING)

5. The more particles in a solution (ions or molecules) the larger the effect on the freezing and boiling point

   1. MORE PARTICLES = BIGGER IMPACT (INCREASING BOILING POINT, DECREASING FREEZING POINT)

As solvent is added: particles get in the way so phase change requires more energy leading to…

1. VAPOR PRESSURE DECREASE,

2. BOILING TEMPERATURE INCREASE,

3. FREEZING POING DECREASE

The impact can be effected by these factors:

1. More concentrated (look at molartiy) = more particles per liter of solution, more annoying particles = more energy needed for phase change

2. More particles = more annoying particles getting in the way, more energy needed to phase change