Assignment 5.06: Solubility and

Concentrations

Solutions

Solution – homogeneous mixtureSolute – Part of solution being dissolvedSolvent – Dissolving medium

Example: Salt waterSolute = salt, Solvent = water

Universal Solvent – Water (many substances dissolve in water)

Practice:1) Lemonade Solute = __________ Solvent = _________2) Air Solute = __________ Solvent = _________

(78% N2, 20% O2, 2% other gases)

3) Dilute Sulfuric acid Solute = __________ Solvent = __________

Dissolving Process

1) The solute particles become separated as the forces of attraction between them are disturbed.

2) The solvent particles move apart as the forces of attraction between them are disturbed.

3) The solvent particles begin attracting the solute particles, and they mix together as new attractive forces are formed.

*- Whether or not a material will dissolve in another is dependent on their attraction for each other. The stronger the attraction between solute and solvent particles, the greater the ability for them to mix and dissolve.

Saturation

Saturated – A solution containing the maximum amount of solute under the given conditions (temperature, pressure)

Unsaturated – A solution containing less solute than a saturated solution under given conditions

Factors Affecting Solubility

Factors Affecting Solubility1) Temperature

a) Solid in a liquid = Solubility increases with increasing temperature. Temperature Increase Kinetic Energy Increases Collisions Increase between solute and solvent Solute particles break apart more quickly

b) Gas in a liquid = Solubility decreases with increasing temperature. Temperature Increase Kinetic Energy Increases Solute particles come in contact with the surface and escape from solution more often

2) Pressurea) Gas in a liquid = Solubility increases with increasing pressure.

Pressure Increase (above a solution in a closed container) Solute particles are “forced” into solution

Factors Affecting Dissolving Rate

1) Surface Areaa) Increase surface area (granules) More exposed solute More collisions between solute and solvent Dissolves faster

2) Stirring/Shaking (Agitation) a) Increase stirring/shaking Solute is dispersed throughout the

solvent More collisions between solute and solvent Dissolves faster

3) Temperaturea) Increase temperature Increase Kinetic Energy (particles are moving faster) More collisions between solute and solvent Dissolves faster

Solution Concentration – Molarity (Sample)

Molarity =

What is the molarity of a solution in which 32.0 g of KCl is dissolved in 525. mL of solution?

Step 1) 32.0 g KCl 1 mol KCl = 0.429 mol KCl 74.551 g KCl

Step 2) 525. mL 1 L = 0.525 L solution 1000 mL

Step 3) Molarity = 0.429 mol KCl = 0.818 M KCl 0.525 L solution

Moles of SoluteLiters of Solution

Solution Concentration – Molarity (Practice)

Molarity =

1) What is the molarity of a solution in which 10.0 g of AgNO3 is dissolved in 500. mL of solution?

2) What is the molarity of a solution in which 25.2 g of NaCl is dissolved in 755 mL of solution?

Moles of SoluteLiters of Solution

Solution Concentration – Percent by Mass (Sample)

Percent by Mass = x 100%

What is the percent by mass of a solution in which 15.0 g of Na2SO4 is dissolved in 850. mL of solvent?

Step 1) 850. mL 1 g solution = 850. g solution 1 mL solution

Step 2) Percent by Mass = 15.0 g Na2SO4 x 100%

15.0 g Na2SO4 + 850. g sol.

= 1.73 % by mass

Mass of SoluteMass of Solution

Solution Concentration – Percent by Mass (Practice)

Percent by Mass = x 100%

1) What is the percent by mass of a solution in which 20.0 g of AgCl is dissolved in 500. mL of solution?

2) What is the percent by mass of a solution in which 25.2 g of CaBr2 is dissolved in 245 g of Water?

Mass of SoluteMass of Solution